jThe  Decomposition  of  Hydrocarbons 

and 

The  Influence  of  Hydrogen  in 
!  Carbureted  Water  Gas  Manufacture 


DISSERTATION 


SUBMITTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIREMENTS 

FOR  THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY 

IN  THE  FACULTY  OF  PURE  SCIENCE 

COLUMBIA  UNIVERSITY  IN  THE 

CITY  OF  NEW  YORK 


BY 


Eugene  Hendricks  Leslie,  B.S. 


NEW  YORK  CITY 
1916 


The  Decomposition  of  Hydrocarbons 

and 

The  Influence  of  Hydrogen  in 
Carbureted  Water  Gas  Manufacture 


DISSERTATION 


SUBMITTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIREMENTS 

FOR  THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY 

IN  THE  FACULTY  OF  PURE  SCIENCE 

COLUMBIA  UNIVERSITY  IN  THE 

CITY  OF  NEW  YORK 


BY 
Eugene  Hendricks  Leslie,  B.S, 


NEW  YORK  CITY 
1916 


rt 


to 


V 


ACKNOWLEDGMENTS 

The  author  wishes  to  express  to  Professor  Milton  C. 
Whitaker  his  sincerest  gratitude  for  his  many  sugges- 
tions and  helpful  criticisms,  and  for  his  encouragement 
and  cooperation  during  the  progress  of  this  work. 

To  Professor  Floyd  J.  Metzger,  Professor  Samuel  A. 
Tucker  and  Dr.  Clive  M.  Alexander  the  author  also 
wishes  to  extend  thanks  for  their  help  and  suggestions. 

EUGENE  H.  LESLIE 

DEPARTMENT  OP  CHEMICAL  ENGINEERING 
COLUMBIA  UNIVERSITY 


342654 


THE  DECOMPOSITION  OF  HYDROCARBONS   AND   THE 

INFLUENCE   OF   HYDROGEN   IN   CARBURETED 

WATER   GAS   MANUFACTURE 

I— HISTORICAL  REVIEW 

The  task  of  reviewing  and  assembling  the  large 
amount  of  material  which  has  been  written  on  the  re- 
actions of  the  hydrocarbons  under  the  influence  of 
heat  is  in  no  sense  an  easy  one.  On  account  of  the 
variety  of  the  materials  which  have  been  worked 
upon,  the  extreme  complexity  of  the  changes  which 
take  place  in  any  case,  the  differences  in  the  types  of 
apparatus  used,  and  the  apparent  inclination  of  many 
writers  to  allow  the  reader  to  do  the  greater  part  of 
the  interpretation  of  the  results,  which  in  many  cases 
is  well  nigh  impossible,  the  presentation  of  this  ma- 
terial in  condensed  form  is  accompanied  by  readily 
appreciated  difficulties.  Such  a  summary  must  neces- 
sarily confine  itself  to  the  work  of  those  who  seem 
to  have  added  most  to  the  knowledge  in  this  field. 

In  the  discussion  which  follows  the  topics  taken 
up  will  be: 

I — The  work  relative  to  the  primary  decomposi- 
tion of  high  molecular  weight  paraffin  and  naphthene 
hydrocarbons. 

II — The  various  ideas  in  regard  to  the  mode  of  re- 
action of  the  products  of  the  primary  decomposition. 

Ill — The  pyrogenic  reactions  of  the  simpler  com- 
pounds such  as  methane,  ethane,  ethylene,  and  sim- 
ilar hydrocarbons. 

IV — Aromatic  hydrocarbons. 

V — The  influence  of  hydrogen  on  these  reactions. 

VI — The  transfer  of  heat  in  gas  machines. 

VII — Our  own  experiments. 

I PRIMARY  DECOMPOSITION 

It  is  evident  that  when  a  high  molecular  weight 
paraffin  splits  up  into  two  simpler  molecules  both 
of  these  cannot  be  saturated  hydrocarbons.  An 
olefin  and  a  paraffin  result. 

It  might  be  thought  that  two  olefins  and  hydrogen 

d) 


£>e- formed.     If  this  were  the  case  the  decomposi- 
tion of  pehtane  would  be  represented: 

£5X112    ^ C2A14    ~T    Carle    ~f"    H2 

If  this  were  the  manner  of  the  decomposition  the 
gases  arising  should  contain  at  least  33  per  cent  of 
hydrogen  whereas  we  know  that  low  temperature 
gases  contain  very  little  hydrogen. 

The  other  possibility  that  two  paraffins  might  re- 
sult with  simultaneous  separation  of  carbon  is  also 
not  the  case  as  can  be  seen  from  the  analysis  of  low 
temperature  oil  gases  shown  graphically  elsewhere 
in  this  paper,  and  also  from  the  fact  that  low  tempera- 
ture oil  cracking  produces,  only  very  small  amounts 
of  carbon.  That  such  a  change  is  possible  at  low  tem- 
peratures, however,  in  a  hydrocarbon  system  of  this 
sort  can  be  seen  from  the  fact  that  McAfee1  in  the 
aluminum  chloride  catalytic  process  obtained  low 
boiling*  saturated  hydrocarbons  with  none  of  the  un- 
saturated  hydrocarbons.  The  carbon  separated  out 
in  the  form  of  a  granular  coky  mass.  Even  when 
the  starting  material  was  unsaturated  the  final  prod- 
ucts were  saturated  hydrocarbons  and  carbon.  That 
.the  course  of  the  reaction  in  the  presence  of  aluminum 
chloride  is  different  from  that  of  the  thermal  de- 
composition at  low  temperatures  is  obvious. 

That  the  primary  decomposition  is  actually  a  break- 
ing down  to  paraffin  and  olefin  has  been  well  estab- 
lished by  the  work  of  investigators  which  will  be  cited 
below,  and  is  borne  out  by  our  own  experiments  which 
will  be  discussed  later. 

The  next  question  which  naturally  arises  is  where 
does  the  long  paraffin  chain  split,  in  the  middle  or 
near  the  -end?  And  if  the  rupture  is  near  the  end 
which  is  the  product  of  low  molecular  weight,  the  olefin 
or  the  paraffin?  In  the  discussion  of  these  questions 
the  work  of  several  investigators  will  be  cited. 

Vohl2  believed  that  the  higher  paraffins  decomposed 
primarily  into  a  paraffin  of  high  molecular  weight 
and  an  olefin  with  few  carbon  atoms.  His  views, 
however,  have  not  been  accepted  and  are  not  in  ac- 
cordance with  the  greater  portion  of  the  experimental 
evidence  recorded  in  the  literature. 
,  Thorpe  and  Young3  heated  solid  paraffins  in  sealed 
tubes,  and  found  that  under  the  combined  influence 

,  »  J.  Ind.  Eng.  Chem.,  1  (1915),  737-741;  Met.  Chem.  Eng.,  13  (1915). 
592-597. 

2  Dingler's  polytech.  J.,  177,  69. 

s  Proc.  Roy.  Soc.,  11,  184-201. 

(2) 


of  heat  and  pressure  a  mixture  of  olefins  and  paraffins 
of  lower  boiling  point  was  obtained.  They  believed 
this  mode  of  decomposition  to  be  general,  but  were 
unable  to  bring  forward  experimental  evidence  as  to 
whether  the  change  gave  rise  to  an  olefin  of  low  molec- 
ular weight  with  a  larger  paraffin  residue,  or  vice  versa. 

Prunier1  found  that  butylene,  propylene,  ethylene, 
and  some  crotonylene  were  formed  when  light  petro- 
leum vapors  were  passed  through  a  glowing  tube. 

H.  E.  Armstrong2  reported  the  finding  of  consid- 
erable quantities  of  amylene  and  hexylene  along  with 
aromatic  hydrocarbons  in  the  compression  liquids 
from  Pintsch  gas  manufacture.  Paraffins  were  not 
present.  A  gaseous  compound  was  dissolved  in 
these  liquids  which  gave  a  bromide  of  the  formula 
C4H6Br4,  and  which,  according  to  Armstrong,  was 
probably  methylallene,  CH3 — CH  =  C  =  CH2. 

Brochet3  identified  normal  butylene,  normal  amylene, 
normal  hexylene,  and  piperylene  in  the  compression 
liquids  from  Pintsch  gas  manufacture. 

Lewes4  found  hexylene  and  heptylene  in  the  tar 
obtained  by  the  cracking  of  Russian  oil. 

Brooks5  examined  a  compression  liquid  from  the 
Pintsch  gas  process  and  found  it  to  contain  48.0  per 
cent  of  unsaturated  products  removable  by  cold  con- 
centrated sulfuric  acid.  The  rest  was  chiefly  ben- 
zene. Experiments  carried  out  by  him  showed  that 
solar  oil  when  treated  at  temperatures  between  430° 
C.  and  600°  C.  yielded  3  to  20  per  cent  of  gasoline 
boiling  below  150°  C.  This  product  was  highly  un- 
saturated. Treatment  with  cold  concentrated  sul- 
furic acid  caused  a  20  per  cent  loss.  When  nickel  was 
used  along  with  the  oil  more  gas  was  produced  and 
the  product  contained  more  unsaturated  hydrocar- 
bons. 

Armstrong  and  Miller6  examined  the  liquid  products 
which  resulted  when  oil  gas  was  compressed,  and 
found  that  it  contained  considerable  quantities  of 
amylene  and  its  next  two  higher  homologs,  but  not  the 
corresponding  paraffins.  This  apparently  is  evidence 
in  favor  of  the  view  that  the  initial  decomposition 
of  the  oil  is  such  as  to  give  rise  to  a  high  molecular 
weight  olefin  and  a  low  molecular  with  paraffin; 

Ber.,  6  (1873),  72. 

/.  Soc.  Ghent.  Ind.,  3  (1884),  462-468. 

Compt.  rend.,  114  (1892).  60. 

J.  'Soc.  Chem.  Ind.,  11  (1892"),  584. 

J.  Frank.  Inst.,  180  (1915),  653-673. 

J.  Chem.  Soc.,  49  (1886),  74-93. 

(3) 


for  if  paraffin  and  olefin  of  nearly  the  same  molecular 
weight  had  been  formed  we  should  expect  that  a  pre- 
ponderance of  paraffins  would  have  been  found  in 
the  liquid  resulting  from  the  compression.  It  is  well 
known  that  the  paraffins  with  carbon  chains  of  three 
atoms  or  over  are  more  stable  with  respect  to  the  in- 
fluence of  heat  than  the  corresponding  olefins. 

Norton  and  Andrews1  passed  vapors  of  hexane  and 
pentane  through  glass  or  porcelain  tubes  15  mm. 
in  diameter  and  70  cm.  long  heated  to  a  bright  red 
heat.  In  their  experiments  on  hexane  a  liquid  col- 
lected in  the  receiver  which  was  approximately  10 
per  cent  by  weight  of  the  hexane  used,  and  which 
contained  unchanged  hexane,  hexylene,  amylene, 
and  a  little  benzene.  The  hexylene  and  amylene 
were  not  present  in  large  amount,  but  this  would 
not  be  expected  when  the  temperature  of  their  experi- 
ments is  taken  into  consideration.  They  found  large 
amounts  of  propylene  and  ethylene  which  they  col- 
lected by  passing  the  gases  through  bromine,  and  these 
hydrocarbons  no  doubt  arose  from  the  secondary 
decomposition  of  amylene. 

J.  F.  Tocher2  destructively  distilled  octane  and  dec- 
ane.  He  says  in  the  discussion  of  his  results  that  they 
"bear  out  that  at  low  temperatures  octane  and  dec- 
ane  are  decomposed  into  ethylene  and  higher  olefins, 
methane,  and  hydrogen,  while  at  higher  tempera- 
tures no  higher  olefins  are  formed,  the  gaseous  prod- 
ucts being  simply  ethylene,  methane,  and  hydrogen." 
Thus  again  emphasis  is  laid  on  the  presence  of  higher 
olefins  without  the  corresponding  paraffins. 

Haber3  studied  the  decomposition  of  normal  hexane 
believing  that  its  mode  of  decomposition  was  similar 
to  that  of  the  still  higher  paraffins.  He  vaporized  the 
hydrocarbons  and  passed  the  vapors  through  a  tube 
1/s  in.  in  diameter  and  25  in.  long  heated  to  tem- 
peratures at  intervals  between  448°  and  800°  C. 
The  low  temperature  was  used  to  avoid  the  secondary 
decomposition  which  plays  so  important  a  part  at  higher 
temperatures.  The  hexane  was  not  appreciably  de- 
composed at  518°  C.  At  600°  to  700°  C.  the  gaseous 
products  contained  slightly  over  50  per  cent  olefins, 
34  to  37  per  cent  saturated  hydrocarbons  (of  which 
approximately  70  per  cent  was  methane)  and  10  to 

1  Am.  Chem.  J.,  8  (1886),  1-9. 

2  J.  Soc.  Chem.  Ind..  13,  231-237. 

3  J.  Gasbel,  39   (1896),  377-382,  395-399,  435-439,  452-455,  799-805, 
813-818,  830-834;  Ber.,  29  (1896),  2691-2700. 

(4) 


13  per  cent  hydrogen.  From  a  number  of  such  ex- 
periments Haber  concluded  that  the  primary  decom- 
position took  place  largely  in  accordance  with  the 
equation  C6Hi4  <  >  C5Hi0  -f-  CH4,  and  from  the  re- 
lations between  the  amounts  of  gaseous  and  liquid 
olefins,  and  the  mean  molecular  weight  of  the  olefins 
in  the  gaseous  state  he  was  led  to  believe  that  a  por- 
tion of  the  amylene  decomposed  into  propylene  and 
ethylene  thus:  C5Hi0  "7"**  C3H6  +  C2H4.  In  any  case 
Haber  was  convinced  that  the  primary  decomposi- 
tion of  the  higher  fatty  hydrocarbons  involved  the 
splitting  off  of  hydrocarbons  of  less  than  three  carbon 
atoms  with  the  formation  of  practically  no  hydrogen. 
The  higher  the  temperature  the  greater  the  tendency 
for  the  splitting  off  to  take  place  near  the  end  of  the 
chain. 

Kramer  and  Spillker1  distilled  a  heavy  hydrocar- 
bon oil  at  450°  C.  and  under  20  atmospheres  pressure. 
Considerable  gas  was  formed  which  contained  20 
per  cent  olefins  and  80  per  cent  methane.  The  liquid 
distillates  contained  large  amounts  of  olefins.  These 
observations  are  in  accordance  with  the  view  that 
the  chief  initial  reaction  is  a  splitting  into  high  molec- 
ular weight  olefins  and  low  molecular  weight  paraffins. 

Engler2  believes  that  the  decomposition  of  high 
molecular  weight  paraffins  begins  at  200  to  250°  C. 
at  ordinary  pressure.  Still  residues  which  he  has 
examined  were  composed  largely  of  olefins  and  their 
polymerization  products.  In  his  study  of  the  crack- 
ing of  a  heavy  Galician  oil  residue  he  found  that  the 
amount  of  olefins  in  the  cracked  distillate  was  high- 
est in  the  high  boiling  fractions,  and  that  the  higher 
the  cracking  temperature  the  higher  the  per  cent 
of  olefins.  It  should  be  remembered  that  the  tempera- 
tures used  were  never  high,  for  the  liquid  phase  was 
always  present.  In  "Das  Erdol,"  page  567,  Engler 
expresses  the  belief  that  at  ordinary  pressure  the  effect 
of  heating  is  to  split  off  low  molecular  weight  hydro- 
carbons from  the  end  of  the  chain,  while  with  heating 
under  pressure  the  tendency  is  for  the  long  chain 
to  split  in  the  middle.  That  there  might  be  some 
such  difference  can  be  seen  from  a  consideration  of 
the  application  of  Le  Chatelier's  principle  to  this 
case. 

Worstall  and  Burwell3  in  a  study  of  the  hydrocar- 

i  Ber.,  33  (1910),  2205. 
5  "Das  Erdol,"  p.  566. 
•Am.  Chem.  J.,  19  (1897),  815-845. 

(5) 


bons  of  the  tars  from  the  decomposition  of  heptane 
and  octane  in  Pintsch  gas  retorts  found  that  though 
the  tars  contained  unchanged  heptane  and  octane, 
they  contained  none  of  the  lower  paraffins.  Unsatura- 
ted  compounds  composed  a  third  of  the  tars.  These 
observations  appear  as  an  excellent  corroboration 
of  the  idea  that  the  primary  decomposition  is  in  large 
part  a  splitting  off  of  a  low  molecular  weight  paraffin 
such  as  methane.  Otherwise  propane,  butane,  pen- 
tahe,  and  hexane  should  have  been  found  in  these 
tars,  for  these  hydrocarbons  are  more  stable  under 
the  influence  of  heat  than  the  corresponding  olefins 
or  the  original  heptane  and  octane. 

Hempel1  passed  oil  vapors  through  an  iron  tube 
at  temperatures  below  700°  to  800°  C.  and  concluded 
from  a  consideration  of  his  gas  analyses  that  the  groups 
splitting  off  were  chiefly  those  of  one  or  two  carbon 
atoms.  The  decomposition  into  methane  and  higher 
molecular  weight  olefins  must  predominate  because 
of  the  high  content  of  methane  in  the  gases  obtained. 
Hempel's  views  are  essentially  in  accord  with  Haber's. 

Hall2  brought  out  well  the  dependence  of  the  mode 
of  primary  decomposition  of  a  long  chain  paraffin 
hydrocarbon  on  the  temperature  and  pressure.  He 
found  that  increase  of  pressure  greatly  diminished  the 
yield  of  fixed  gases,  *.  e.,  methane,  etc.  Tempera- 
ture was  of  great  importance.  At  560°  C.  a  change 
of  20°  made  a  difference  of  50  per  cent  in  the  gas  pro- 
duction, and  a  difference  in  the  gravity  of  the  liquid 
boiling  below  a  certain  point,  the  greatest  difference 
being  in  the  unsaturated  portion.  A  40°  C.  tempera- 
ture change  made  as  much  as  40  per  cent  difference  in 
the  unsaturated  portion.  Distillates  containing  from 
30  per  cent  to  90  per  cent  unsaturated  hydrocarbons 
can  be  produced  by  changing  no  other  condition  than 
.the  temperature.  These  facts  mean  that  the  hydro- 
carbon chain  can  break  at  any  point.  The  reactions 
which  actually  take  place  depend  on  thev  conditions. 
It  is  natural  to  suppose  that  increase  of  pressure  would 
tend  to  give  precedence  to  those  reactions  whose  prod- 
ucts occupy  the  least  volume,  i.  e.,  a  splitting  near 
the  middle  of  the  chain  giving  liquid  products.  The 
large  increase  in  the  percentage  of  olefins  in  the  liquid 
products  with  rise  of  temperature  indicates  that  the 
higher  temperatures  favor  decomposition  near  the  end 
of  the  chain,  for  otherwise  the  paraffins  which  are  more 

1  J.  Gasbel.  53  (1910),  53-58,  77-83,  101-105,  137-141,  155-165. 

2  Gas  World,  62  (1915),   187,  el  seq. 

(6) 


stable  than  the  corresponding  olefins  would  predom- 
inate in  the  liquid  products. 

Ipatiew  and  Dowgelewitsch1  found  that  hexane 
was  decomposed  at  710°  C.  yielding  40  to  50  per  cent 
hydrocarbons  of  the  CMH2n  series,  8  to  14  per  cent 
hydrogen,  and  40  per  cent  paraffins.  Hexamethylene 
heated  for  some  time  at  500  to  510°  C.  and  under  70 
atmospheres  pressure  gave  a  quantity  of  gas  which 
was  largely  methane  and  hydrogen.  The  liquid  'prod- 
ucts contained  considerable  amounts  of  olefins,  and 
also  methyl  cyclopentane. 

It  seems  that  the  mode  of  the  pyrogenic  decomposi- 
tion of  the  naphthenes  is  not  so  different  from  that 
of  the  paraffins,  with  a  few  added  complications  such 
as  rearrangement  to  the  more  stable  five-carbon  ring 
and  dehydrogenation  to  aromatics. 

Burgess  and  Wheeler2  found  a  considerable  evolu- 
tion of  higher  olefins  from  coal  up  to  350°  C.  They 
believed  that  these  hydrocarbons  arose  from  the  de- 
composition of  a  paraffin  or  other  similar  long  chain 
hydrocarbon. 

Brooks,  Bacon,  Padgett,  and  Humphrey,3  in  dis- 
cussing the  cracking  of  higher  hydrocarbons,  pointed 
out  that  the  fatal  difficulty  with  all  processes  at- 
tempting to  produce  gasoline  from  the  higher  hydro- 
carbons was  the  large  percentage  of  olefins  contained 
in  the  product.  According  to  these  authors  this  fig- 
ure will  vary  from  20-50  per  cent,  depending  on  the 
temperature  at  which  the  oil  is  cracked.  An  inter- 
esting observation  which  bears  on  the  mechanism 
of  the  primary  decomposition  was  that  the  gases  evolved 
during  the  distillation  of  paraffin  under  100  Ibs.  pressure 
at  temperatures  between  350°  and  450°  C.  consisted 
of  75—62  per  cent  saturated  hydrocarbons,  25  to  37 
per  cent  olefins,  with  o.o  to  3  per  cent  hydrogen. 
The  saturated  hydrocarbons  were  not  examined,  but 
as  only  the  lower  paraffins  are  gaseous,  and  as  it  is 
common  experience  that,  where  the  gaseous  paraffins 
are  formed  at  all,  methane  always  predominates  it  is 
not  unfair  to  assume  that  a  large  proportion  of  the 
gases  obtained  here  was  methane. 

Pressure  would  be  unfavorable  to  such  a  reaction 
as 

CnH2n+2  — >•  Ctt_,H2M_2  +  CH4. 

Nevertheless  such  reactions  constitute    the    most  im- 

1  Ber.,  44  (1911),  2987-2992. 

2  J.  Chem.  Soc.,  105  (1914),  131-140. 

»  J.  Ind.  Eng.  Chem.,  7  (1915),   180-185. 

(7) 


portant  chemical  change  taking  place  when  these 
higher  hydrocarbons  are  heated  even  at  100  Ibs. 
pressure  and  only  450°  C.  The  conclusion  then  must 
be  that  the  change  in  concentration  on  account  of 
increased  pressure  has  a  more  important  effect  than 
the  shifting  of  the  equilibrium  point  of  the  reaction. 

The  most  exact  work  on  the  separation  of  the  indi- 
vidual hydrocarbons  resulting  from  the  decomposi- 
tion of  the  hydrocarbons  of  high  molecular  weight  is 
that  of  Burrell,  Seibert,  and  Robertson.1  By  a  series 
of  careful  fractionations  at  low  temperatures  these 
investigators  have  determined  the  percentages  of  the 
various  components  in  Pittsburgh  coal  gas  and  water 
gas.  The  following  table  shows  their  results: 

CARBURETED 

COMPONENT                   COAL  GAS  WATER  GAS 

Carbon  dioxide 1.4  4.8 

Oxygen 0.7  (a) 

Carbon  monoxide 7.9  29 .8 

Hydrogen 50.6  32.0 

Methane 31.1  13.1 

Ethane 0.9  2.9 

Ethylene 2.1  9.8 

Propylene 0.3  2.8 

Butylene 0.1  1.7 

Butane 

Propane 0.3 

Benzene(fc) 1.4  15 

Nitrogen 3.5  1.3 


Total 100.0  per  cent        100. 0  per  cent 

(a)  Results  calculated  to  air-free  basis. 

(b)  Benzene  or  vapor  having  an  inappreciable  pressure  at  — 78°  C. 

The  notable  feature  of  these  results,  so  far  as  their 
bearing  on  the  primary  decomposition  of  hydrocar- 
bons is  concerned,  lies  in  the  fact  that  the  percentages 
of  olefins  were  always  higher  than  the  percentages 
of  paraffins  of  the  same  number  of  carbon  atoms. 
Thus  in  water  gas  there  was  2 . 8  per  cent  propylene, 
but  only  o .  3  per  cent  propane  and  i .  7  per  cent  butyl- 
ene,  but  only  traces  of  butane.  When  the  relative 
stability  of  these  hydrocarbons  is  kept  in  mind,  and 
also  the  temperatures  at  which  these  gases  were  made, 
these  results  appear  as  good  evidence  that  tinder  water 
gas  carbureter  and  superheater  conditions  the  splitting 
off  of  low  molecular  weight  paraffins  with  formation 
of  high  molecular  weight  olefins  is  the  chief  primary 
reaction. 

Egloff  and  Twomey2  have  cracked  a  gas  oil  de- 
rived from  Pennsylvania  crude  petroleum  at  atmos- 
pheric pressure,  and  at  temperature  intervals  of  50° 
C.  between  450°  C.  and  800°  C.  In  the  cracked  oils 
it  was  found  that  the  per  cent  of  unsaturated  com- 

1  U.  S.  Bur.  of  Mines,   Tech.  Paper,   104. 

2  Met.  Chem.  Eng.,  14  (1916),  247-250. 

(8) 


pounds  increased  with  the  temperature.  In  the  dis- 
tillation cut  to  150°  C.  the  per  cent  of  unsaturateds 
reached  a  maximum  of  44  per  cent  at  550°  C.  and  de- 
creased to  practically  o  per  cent  at  800°  C.  Thefrac- 
tionation  of  the  cracked  oils  was  made  in  six  cuts: 
95°to  120°  C.,  120°  to  150°,  i7o°to  230°,  230°  to  270°, 
and  270°  to  tar.  In  the  first  of  these  cuts  it  was 
found  that  the  percentage  of  unsaturateds  reached 
a  maximum  at  550°  to  600°  C.  while  in  the  latter 
three  cuts  there  was  a  steady  increase  with  tempera- 
ture in  the  proportion  of  unsaturateds.  The  authors 
believed  that  the  decrease  in  olefin  formation  might 
be  accounted  for  by  polymerization  of  olefins  to 
naphthenes  which  in  turn  go  to  aromatics,  and  secondly 
direct  polymerization  of  olefins  to  aromatics.  An- 
other factor,  no  doubt,  contributes  in  large  degree  to 
the  observed  diminution  in  the  per  cent  of  olefins  in 
the  low  boiling  cuts  with  increase  in  temperature, 
namely  decomposition  of  the  olefins  to  gaseous  prod- 
ucts of  lower  molecular  weight.  This  is  discussed 
more  at  length  elsewhere  in  this  paper. 

The  results  of  Egloff  and  Twomey  are  just  those 
which  would  be  expected  if  it  is  considered  that  at 
low  temperatures  the  tendency  of  the  higher  molec- 
ular weight  paraffins  is  to  split  into  paraffin  and  olefin 
of  nearly  equal  chain,  while  at  higher  temperatures 
the  primary  decomposition  is  into  high  molecular 
weight  olefin  and  low  molecular  weight  paraffin. 

II SECONDARY    DECOMPOSITION    OF    HYDROCARBONS 

Two  classes  of  secondary  reactions  must  be  taken 
into  account,  first  those  which  result  in  the  breaking 
down  of  the  hydrocarbon  molecules  to  hydrocarbons 
of  lower  molecular  weight,  and  second  those  synthetic 
reactions  which  give  rise  to  more  complex  but  more 
stable  hydrocarbons. 

In  reviewing  the  work  bearing  on  the  primary  de- 
composition of  paraffin  hydrocarbons  of  high  molecu- 
lar weight  it  has  been  shown  that  the  greater  portion 
of  the  experimental  evidence  points  to  a  splitting  of 
the  carbon  chain  with  formation  of  olefin  and  paraffin, 
and  that  conditions  determine  where  the  rupture 
takes  place — low  temperature  and  high  pressure 
tending  to  favor  the  splitting  near  the  middle  of  the 
chain  while  at  lower  pressures  and  higher  tempera- 
tures the  breaking  off  of  low  molecular  weight  hydro- 
carbons, such  as  methane,  ethane,  and  ethylene, 
but  particularly  methane  and  ethane,  becomes  the 
important  reaction. 

(9) 


The  members  of  the  paraffin  series  down  to  butane 
in  all  probability  follow  some  such  mode  of  reaction 
as  this.  The  first  problem  to  be  considered  in  the 
study  of  the  secondary  reactions,  then,  is  the  fate 
of  the  high  molecular  weight  olefins  which  arise. 

If,  for  the  sake  of  simplicity,  pentylene,  CH2CH2- 
CH2CH  =  CH2,  be  regarded  as  typical  of  the  higher 
olefines  we  may  list  a  few  of  the  possible  reactions  as 
follows: 

(1)  CH3CH2CH2CH=CH2  ^± 

CH3CH=CH2  +  CH2=CH2 

(2)  CH3CH2CH2CH=CH2^±1      .. 

CH4 .+  CH3— C^C— CH3 
/CH2 — CH2 

(3)  CH3CH2CH2CH=CH2    ^±     CH/  | 

\CH?—  CH2 

(4)  CH3CH2CH2CH=CH2  +  H2  ^± 

CH3CH2CH2CH2CH3 

(5)  Condensation 

It  is  not  to  be  imagined  that  any  one  of  these  reac- 
tions is  the  sole  reaction,  nor  is  this  to  be  regarded  as 
in  any  sense  a  complete  list  of  the  possible  concurrent 
reactions.  The  extent  to  which  any  or  all  of  these 
changes  take  p'ace  is  dependent  on  the  temperature, 
pressure  and  concentrations.  It  is  in  an  effort  to  dis- 
cuss the  extent  to  which  each  comes  into  play,  and 
the  effect  of  varying  conditions  that  the  work  is  re- 
viewed bearing  on  this  phase  of  the  subject  and  that 
later  our  own  experiments  are  considered. 

Engler  and  Routala1  heated  350  g.  of  amylene  in 
sealed  glass  tubes  at  325°  C.  for  32  days.  About  ten 
liters  of  gas  were  produced  of  which  over  90  per  cent 
was  paraffin,  7 . 5  per  cent  hydrogen,  and  the  rest 
olefins.  The  liquid  product  contained  a  great  variety 
of  hydrocarbons  of  the  paraffin  and  polymethylene 
series.  Also  the  higher  boiling  portions  contained 
compounds  of  lower  hydrogen  content  than  the  cyclo- 
paraffins. 

The  presence  of  the  gaseous  paraffin  compounds 
and  the  high  boiling  compounds  with  more  than  one 
double  bond  can  be  explained  if  it  is  assumed  that 
the  amylene  splits  into  methane  and  divinyl,  CH2= 
CH — CH=CH2,  or  into  methane  and  crotonylene, 
reactions  analogous  to  (2)  above. 

CH3v 

V=CH—  CH3  ^±  CH4  +  CHs— C=C— CH3 
CH/  Crotonylene 

»  Ber.,  42  (1909),  4620-31. 

(10) 


The  divinyl,  or  crotonylene,  under  the  influence  of 
heat  and  pressure,  might  easily  polymerize  to  high 
molecular  weight  compounds  of  low  hydrogen  content. 

The  naphthenic  compounds  in  all  probability  re- 
sulted from  the  polymerization  of  the  decomposition 
products  of  amylene,  such  as  ethylene  and  propylene 
or  the  substituted  ethylenes  and  propylenes;  or  by  a 
rearrangement  of  the  amylene  molecule  as  in  reac- 
tion (3). 

Engler1  stated  that  long  chain  olefins  split  easily 
into  ethylene.  The  importance  of  reactions  result- 
ing in  higher  molecular  weight  hydrocarbons  of  lower 
hydrogen  content  was  emphasized.  Naphthenes  were 
found  in  the  product  from  the  heating  of  still  residues 
at  300°  C.,  and  since  these  compounds  were  not  pres- 
ent in  the  still  residues  originally,  Engler  concluded 
that  they  were  formed  by  polymerization  of  ethylenes. 
He  was  of  the  opinion  that  direct  closing  of  the  olefin 
chain  did  not  take  place,  but  this  was  not  proved  by 
experimental  evidence. 

Worstall  and  Bur  well2  have  worked  on  oil  gas  tars 
in  an  effort  to  determine  whether  or  not  naphthenes 
were  present.  They  mentioned  that  the  absence  of 
naphthenes  in  residues  from  nitration  or  sulfonation 
is  not  evidence  that  there  were  no  naphthenes  in 
the  original  tar,  for  the  naphthenes  nitrate  to  nitro- 
hydrobenzenes.  Such  compounds  have  been  ob- 
tained by  the  use  of  dilute  nitric  acid.3  From  distilla- 
tion methods  and  specific  gravity  tests  the  authors 
concluded  that  their  oil  gas  tars  contained  no  naph- 
thenes. 

It  is  to  be  kept  in  mind  here  that  oil  gas  in  the  Pintsch 
gas  process  is  made  at  temperatures  of  850°  to  900°  C.,. 
and  it  is  probable  that  this  accounts  for  the  differ- 
ence between  the  results  of  these  authors  and  those  of 
Engler  whose  work  was  carried  out  at  lower  tempera- 
tures; i.  e.,  between  300°  and  400°  C. 

Haber,4  on  the  other  hand,  was  convinced  by  a  study 
of  the  combustion  data  of  oil  gases  made  from  hexane 
at  temperatures  of  600°  C.  and  above  that  naphthenes 
were  present.  He  also  believed  that  crotonylene  was 
formed  in  small  amounts  by  the  splitting  off  of  methane 
from  amylene.  Emphasis  was  laid  on  the  synthetic 
reactions  such  as  the  building  up  of  high  molecular 

1  Ber.,  SO  (1897),  2908. 

2  Am.  Chem.  J .,  19  (1897),  815-845. 

3  Ber.,  25  (1892),   107-108;  28  (1895),  577-578. 

<  J.  Gasbel,  39   (1896),  377-382,  395-399,  435-439,  452-455,   799-805. 
813-818,  830-834. 

(II) 


weight   compounds  by  the   combination   of  "free   un- 
saturated  residues." 

H.  E.  Armstrong1  found  a  gas  dissolved  in  the  com- 
pression liquids  from  oil  gas  manufacture  which  gave 
a  bromide  of  the  composition  C4H6Br4,  and  which  he 
believed  to  be  methylallene,  CH3 — CH=C=CH2. 

Armstrong  and  Miller,2  in  the  examination 
of  similar  liquids,  found  olefins  of  the  type  CMH2M_ 2- 
Vinyl  ethylene,  CH2=CH— CH=CH2,  was  identified. 

A.  Harzer3  commented  on  the  fact  that  there  was 
a  considerable  proportion  of  diolefins  among  the 
hydrocarbons  of  coal  and  coal  tar. 

Jones  and  Wheeler4  made  note  of  their  observation 
that  one-fifth  by  weight  of  the  tar  formed  in  their 
vacuum  distillations  of  coal  at  low  temperatures 
was  composed  of  olefins,  the  greater  part  of  which 
was  richer  in  carbon  than  the  mono-olefins.  This 
appears  an  excellent  evidence  that  the  decomposi- 
tion of  the  higher  olefins  into  methane  and  diolefins 
or  substituted  acetylenes  is  really  one  of  the  reactions 
in  the  course  of  the  breaking  down  of  these  long  chain 
olefins;  for  the  conditions  used  here,  i.  e.,  low  tempera- 
ture and  low  pressure,  are  those  which  tend  to  pre- 
serve intermediate  products,  and  not  those  which 
would  be  likely  to  give  rise  to  diolefins  through  syn- 
thetic reactions. 

W.  A.  Noyes,  W.  M.  Blinks,  and  A.  V.  H.  Morey5 
made  oil  gases  at  comparatively  low  temperatures 
in  a  checkerbrick  filled  machine.  The  gases  were 
analyzed  for  olefins  by  passing  them  through  bromine 
water,  and  subsequently  fractionating  the  bromides 
formed.  In  this  manner  they  found  that  of  the  28.  i 
per  cent  olefins  present  16.2  per  cent  was  ethylene 
and  11.9  per  cent  propylene. 

Norton  and  Andrews,6  in  their  work  on  the  pyro- 
genic  decomposition  of  hexanes  and  pentanes,  passed 
the  gases  through  bromine  dissolved  in  carbon  disul- 
fide.  The  liquid  bromides  so  formed  were  found  to 
be  ethylene  and  propylene  dibromides  in  nearly  equal 
proportion.  This  observation  and  that  of  Noyes, 
Blinks,  and  Morey,  is  entirely  in  accord  with  the 
belief  that  reactions  such  as  the  first  one  mentioned 
in  the  list  above  take  place, 

1  J.  Soc.  Chem.  Ind.,  3  (1884),  462-468. 

2  /.  Chem.  Soc.,  49  (1886),  74-93. 

3  Gas  World,  59  (1913).  405. 

*  /.  Chem.  Soc.,  105  (1914),  140-151,  2562-2565. 

•  J.  Am.  Chem.  Soc.,  16  (1894),  688-697. 
s  Am.  Chem.  J.,  8  (1886),  1-9. 

(12) 


CsHio  ^ CsHe  -f-  CoH4 

i.  e.,  a  splitting  of  higher  olefins  into  lower  olefins. 
Norton  and  Andrews  also  found  that  there  was  formed 
a  solid  bromide  of  the  composition  C4H6Br4,  which  was 
evidently  the  bromide  of  divinyl  or  crotonylene  rather 
than  ethyl  acetylene,  since  the  hydrocarbons  passed 
through  a  solution  of  ammoniacal  cuprous  chloride 
before  being  led  into  the  bromine  solution.  Ethyl 
acetylene  would  have  formed  a  copper,  compound, 
and  thus  have  been  removed. 

That  the  higher  olefins  are  intermediate  between 
the  paraffins  and  the  low  molecular  weight  gaseous 
compounds  can  be  seen  by  a  study  of  some  further 
work  of  Norton  and  Andrews.  When  hexane  was 
passed  through  a  15  mm.  diameter  glass  tube  at  700° 
C.,  and  the  products  collected  it  was  found  that  a 
large  portion  of  the  hexane  passed  through  unchanged. 
But  the  liquid  which  was  collected  also ,  contained  a 
mixture  of  butylene,  amylene,  and  hexylene.  The 
bromides  obtained  by  passing  the  gases  through 
bromine  in  carbon  disulfide  were  propylene  dibromide, 
crotonylene  dibromide,  but  no  ethylene  dibromide. 
At  higher  temperatures  the  decomposition  of  isohexane 
gave,  beside  the  liquid  products,  gaseous  hydrocar- 
bons which  proved  to  be  largely  propylene  and  croton- 
ylene with  smaller  amounts  of  ethylene.  Similar 
results  were  obtained  when  pentane  was  pyrogenically 
decomposed^. 

The  statement  as  to  the  absence  of  ethylene  in  the 
700°  C.  gases  from  hexane  should,  as  judged  from 
general  experience,  be  accepted  with  reservations. 
However,  it  must  be  kept  in  mind  that  700°  C.  as 
measured  and  applied  to  a  certain  kind  and  size  of 
apparatus  may  give  results  similar  to  those  of  very 
different  temperatures  in  a  different  apparatus  used 
by  another  observer. 

Lewes1  decomposed  Russian  oil  in  a  short  retort 
at  500°  C.  in  order  to  study  the  early  stages  of  the  de- 
composition of  hydrocarbons.  He  found  the  paraffins 
and  olefins  present  in  nearly  equal  proportions  in  the 
gases.  Increase  of  temperature  diminished  the  per 
cent  of  olefins.  As  the  temperature  went  up  the 
paraffins,  too,  reacted  secondarily,  but  this  was  with 
formation  of  methane  so  that  the  actual  percentage 
of  paraffin  in  the  gas  did  not  decrease,  but  increased. 

Hempel2    was    evidently    of    the    opinion    that    the 

1  J.  Soc.  Chem.  Ind.,  11  (1893),  584-590. 

«  J.  Gasbel,  53  (1910),  53-58,  77-83,   101-105,   137-141,  155-165. 

(13) 


higher  olefins  changed  rather  easily  into  ring  com- 
pounds, and  pointed  to  the  considerable  quantity  of 
these  latter  compounds  which  were  contained  in  oil 
gas  tars.  His  experimental  work  showed  that  when 
oils  were  cracked  in  atmospheres  of  hydrogen  con- 
siderable hydrogen  was  actually  absorbed,  and  that 
the  yields  of  methane,  ethane  and  ethylene  per  unit 
weight  of  oil  were  larger.  His  observations  are  dis- 
cussed more  at  length  elsewhere  in  this  paper,  but  it 
should  be  noted  here  that  hydrogenation  of  these 
higher  olefins  is  not  an  improbable  reaction. 

W.  Ipatiew1  studied  the  polymerization  of  ethylene 
and  some  of  its  homologs.  At  380°  to  400°  C.  and 
70  atmospheres  pressure  the  polymerization  of  ethylene 
is  very  rapid.  The  lower  boiling  fractions  of  the 
products  contained  paraffins,  and  the  higher  boiling 
fractions  olefins  and  polymethylenes.  No  benzene 
hydrocarbons  were  obtained.  The  higher  fractions 
also  contained  some  hydrocarbons  of  higher  carbon 
percentages  and  lower  hydrogen  content  than  the 
C2H2w  series.  Isobutylene  yielded  products  analogous 
to  those  obtained  from  ethylene  except  that  the  hydro- 
carbons richer  in  carbon  than  the  mono-olefins  were 
not  present.  Ipatiew  believed  that  condensation  to 
hexamethylene  was  the  first  step  in  all  these  reac- 
tions. 

The  work  of  Burrell,  Seibert  and  Robertson2  has 
already  been  referred  to  in  our  discussion  of  the  primary 
decomposition  of  hydrocarbons.  Further  valuable 
conclusions  can  be  drawn  from  it,  however,  which 
concern  the  changes  undergone  by  the  high  molecular 
weight  olefins.  The  authors  found  that  Pittsburgh 
carbureted  water  gas  contained  15.9  per  cent  illumi- 
nants,  and  Pittsburgh  coal  gas  3 .  9  per  cent  illuminants. 
The  following  table  shows  the  proportions  of  the 
various  components  which  go  to  make  up  these  totals: 


COMPONENT 
Ethylene  

COAL  GAS 
53.8 

CARBURETED 
WATER  GAS 
60.9 

Propylene  
Butylene  

7.7 
2.6 

17.4 
10.6 

Propane  
Butane 

1.8 

Benzene  (a)  

35.9 

9.3 

(a)   Vapors  having  an  inappreciable  pressure  at  — 78°  C. 

The  proportions  of  ethylene,  propylene  and  butylene 
are  notable.  These  results  may  be  interpreted  as. 
indicating  that  reactions  such  as  C5Hi0  ~^~>  C3H6  + 

1  Ber.,  44  (1911),  2978-2987. 

2  ;U.  S.  Bureau  of  Mines,  Tech.  Paper,  104. 

(14) 


C2H4  actually  play  an  important  part  in  the  breaking 
down  of  the  higher  olefins. 

No  mention  was  made  by  Burrell,  Seibert  and  Rob- 
ertson of  the  naphthenes.  The  hexamethylene  com- 
pounds boil  from  81°  C.  up,  and  might  pass  largely 
into  the  water  gas  tar.  A  portion  of  the  component 
marked  benzene  in  the  above  table  may  easily  have 
been  hexamethylene.  Pentamethylene,  however, 
boils  at  49°  C.,  and  if  it  were  formed  in  significant 
amounts  it  should  be  found  in  the  gases.  Apparently, 
therefore,  compounds  of  this  class  are  not  formed  in 
large  amount  when  the  hydrocarbons  undergo  a  de- 
composition under  the  conditions  of  carbureted  water 
gas  manufacture. 

SUMMARY — It  seems,  then,  that  the  chief  reaction 
undergone  by  these  high  molecular  weight  olefins 
is  a  splitting  into  lower  molecular  weight  olefins. 
A  decomposition  into  methane  and  compounds  with 
two  double  bonds  or  one  triple  bond  also  takes  place. 
The  intramolecular  change  of  olefins  into  cycloparaffins 
is  possible,  but  from  the  evidence  available  it  is  diffi- 
cult to  state  what  proportion  of  the  naphthene  forma- 
tion must  be  ascribed  to  this  reaction.  Hydrogena- 
tion  of  olefins  takes  place  to  some  extent.  Poly- 
merization of  olefins  to  naphthenes  occurs,  also  poly- 
merization of  the  high  molecular  weight  unsaturated 
compounds  to  tarry  compounds. 

Ill TERTIARY    DECOMPOSITION 

The  problem  now  becomes  one  of  studying  the  re- 
actions of  the  hydrocarbons,  which  are  formed  in  the 
primary  and  secondary  decompositions  of  the  paraffins. 
These  products  are  ethylene,  propylene,  diolefins, 
acetylenes,  naphthenes,  methane,  ethane,  propane, 
and  the  high  molecular  weight  tarry  compounds. 
The  discussion  of  the  changes  which  these  hydrocar- 
bons undergo  separately  may  appear  fundamentally 
wrong  in  view  of  the  fact  that  in  the  hydrocarbon 
system  undergoing  change  these  reactions  are  all 
interlocked  and  related  in  a  most  complex  manner. 
However,  it  is  just  on  account  of  this  complexity 
that  the  manner  of  presentation  of  the  material  which 
follows  has  been  chosen — that  is  a  consideration  of 
the  reactions  of  the  separate  hydrocarbons.  Before 
turning  to  such  a  discussion,  however,  it  is  desired 
to  point  out  a  few  things  in  connection  with  such  hy- 
drocarbon systems  as  a  whole. 

The  earliest  attempt  to  elucidate  in  anything  like 

d5) 


a  comprehensive  manner  the  changes  taking  place 
in  a  hydrocarbon  system  was  made  by  Berthelot.1 
He  heated  hydrocarbons  in  a  retort,  and  also  by  pass- 
ing them  through  a  tube.  From  rather  meager  data 
on  a  few  of  the  lower  molecular  weight  hydrocarbons 
a  theory  of  thermal  decomposition  was  worked  out. 
Berthelot  found  that  ethylene  and  hydrogen  when 
heated  in  a  retort  gave  some  ethane,  and  that  ethane 
formed  ethylene  in  small  quantities.  Ethylene  was 
formed  from  acetylene  and  hydrogen.  Ethylene  alone 
gave  small  amounts  of  acetylene  and  ethane;  and 
liquid  products  of  the  formula  of  crotonylene  re- 
sulted when  acetylene  and  ethylene  were  heated  to- 
gether. When  the  gases  were  passed  through  the 
tube  methane  gave  acetylene,  olefins,  ethane,  naph- 
thalene, and  tar.  From  these  experiments  Berthelot 
concluded  that  two  types  of  reactions  were  at  work — 
reactions  of  decompositions,  and  synthetic  reactions. 
The  breaking  down  and  building  up  changes  com- 
peted with  each  other  and  a  complex  equilibrium 
was  supposedly  established. 

Berthelot's  work  has  been  criticized  by  Haber  on 
the  ground  that  conclusions  could  not  be  drawn  re- 
garding hydrocarbon  reactions  in  general  from  a  study 
of  a  few  of  these  simple  hydrocarbons  because  they 
constitute  a  special  case.  For  instance,  ethylene 
cannot  split  open  a  carbon  bond  without  completely 
disrupting  the  molecule,  whereas  a  long  chain  olefin  can 
easily  break  open  in  this  fashion.  Furthermore,  Ber- 
thelot heated  these  substances  in  a  closed  retort.  These 
conditions  are  obviously  not  those  which  should  be 
chosen  for  a  study  of  the  mechanism  of  the  reactions,, 
for  such  heating  would  give  only  those  products  which 
stand  long  heating,  and  not  those  which  might  have 
been  formed  transitorily.  Also  Berthelot's  equi- 
librium idea  is  criticized  by  Haber  for  the  reason 
that  it  would  necessitate  the  presence  of  almost  every 
conceivable  hydrocarbon,  whereas,  though  the  sys- 
tem is  complex  enough,  it  does  not  exhibit  such  a 
heterogeneous  composition  as  this. 

That  Haber's  criticisms  of  Berthelot's  experimental 
methods  and  of  his  general  conclusions  are  well  placed 
can  be  seen  from  a  consideration  of  recent  work 
and  also  from  the  results  of  the  experimental  work, 
recorded  in  this  paper. 

Whitaker   and   Alexander2   have   shown   that    when 

1  Ann.  chim.  phys.,  67,  iii   (1863),  53;  9,  iv   (1866),  413,  455;  12,  iv  • 
(1867),  5,  122;  16,  iv  (1869),  143,  148,  153,  162. 

2  J.  Ind.  Eng.  Chem.,  7  (1915),  484-495. 

(16) 


paraffin  hydrocarbons  are  cracked  at  temperatures 
of  1400°  to  1600°  C.  the  olefins  no  longer  exist,  though 
the  gases  still  contain  approximately  2%  of  methane. 
If  the  oil  rate  was  still  further  decreased  the  methane 
disappeared  and  carbon  and  hydrogen  were  the  only 
products. 

It  is  generally  recognized  that  the  most  stable  gaseous 
hydrocarbons  are  methane,  ethane  and  ethylene. 
Ethane  is  formed  in  much  smaller  amount  than  either 
of  the  other  two,  hence  even  though  it  may  be  more 
stable  than  ethylene  the  latter  persists  longer  in  de- 
tectable amounts  because  it  was  originally  present 
in  larger  proportion.  Any  hydrocarbon  system  heated 
above  700°  C.  will  tend  toward  these  products,  and 
if  given  time  these  gases,  along  with  carbon  and 
hydrogen,  will  be  the  chief  products.  With  the  lapse 
of  more  time  the  ethane  and  ethylene  decompose 
with  formation  of  methane,  carbon  and  hydrogen, 
which  are  the  ultimate  products.  The  methane 
equilibrium  is  discussed  elsewhere  in  this  paper,  and 
it  is  seen  that  methane  exists  in  quantity  only  at  those 
temperatures  below  750°  to  800°  C. 

A  gaseous  hydrocarbon  system  is  thus  not  really 
in  equilibrium.  Rather  the  condition  of  such  a 
system  may  be  compared  to  that  of  a  mixture  of 
hydrogen  and  oxygen  gases  at  temperatures  of  200° 
to  300°  C.  The  equilibrium  condition  of  such  a  sys- 
tem is  practically  a  complete  union  forming  water, 
but  the  speed  of  the  reaction  2H2  +  O2  — >  2H2O 
is  so  small  at  these  temperatures  that  the  system 
might  easily  be  thought  to  be  in  equilibrium,  i.  e., 
in  that  condition  which  is  independent  of  the  further 
passage  of  time. 

Even  though  it  has  been  established  that  a  true 
condition  of  equilibrium  does  not  exist  there  is  still 
an  interdependence  of  reactions  in  a  hydrocarbon 
system.  This  idea  has  been  elaborated  by  Whitaker 
and  Rittman.1 

The  reactions  which  form  the  lower  molecular 
weight  hydrocarbons  are  in  general  more  rapid  in 
their  progress  than  the  reactions  of  decomposition  of 
these  lower  hydrocarbons.  Methane,  in  particular, 
is  stable  under  the  action  of  heat  at  those  tempera- 
tures which  are  used  in  the  various  apparatus  used 
in  the  manufacture  of  gas.  Thus  those  reactions 
which  result  in  the  formation  of  methane  and  ethylene 
reach  a  condition  nearly  corresponding  to  equilibrium 

1  J.  Ind.  Eng.  Chem.,  6  (1914).  383-392,  472-479. 
(17) 


proportions  on  account  of  the  slow  decomposition  of 
ethylene  and  methane,  but  the  system  as  a  whole 
cannot  be  regarded  as  in  equilibrium. 

In  considering  the  discussion  of  the  reactions  of  the 
individual  hydrocarbons  the  effect  of  the  presence 
of  ttie  end-products  of  a  particular  reaction  must 
always  be  kept  in  mind.  Also  the  changing  concen- 
tration conditions  as  the  gas  volume  increases  with 
the  progress  of  the  changes  involved  must  not  be 
forgotten. 

REACTIONS    OF    METHANE 

The  study  of  the  influence  of  heat  at  various  tem- 
peratures on  the  hydrocarbon  methane  has  usually 
been  made  with  the  idea  in  mind  of  finding  the  equi- 
librium proportions  of  methane  and  hydrogen  in  the 
system  carbon-hydrogen-methane. 

The  equilibrium  proportions  are  never  even  approx- 
imated in  experiments  made  after  the  manner  of 
those  discussed  in  the  latter  part  of  this  paper,  nor 
under  the  conditions  maintained  in  the  technical 
production  of  coal,  oil,  and  water  gas.  The  preserva- 
tion of  methane  is  desired  in  all  these  cases,  for  its 
decomposition  into  carbon  and  hydrogen  means  loss 
of  valuable  carbon  from  the  gas  and  the  production 
of  gases  high  in  hydrogen  which  are  unsuited  for  dis- 
tribution. Hence  the  studies  of  the  methane  equi- 
librium are  of  interest  only  in  so  far  as  they  indicate 
the  tendency  of  methane  to  decompose  under  certain 
temperature  conditions. 

Mayer  and  Altmayer1  studied  the  methane  equi- 
librium between  475°  and  625°  C.,  and  found  that' 
below  625°  C.  appreciable  quantities  of  methane 
were  stable.  They  deduced  a  mathematical  expression 
by  means  of  which  they  extrapolated  their  experi- 
mental results  to  250°  C.  on  one  hand  and  850°  C. 
on  the  other.  Finding  that  at  850°  C.  the  calculated 
percentage  of  methane  in  equilibrium  with  carbon 
and  hydrogen  would  be  only  1.59,  they  stated  that 
at  temperatures  as  high  as  1200°  C.  no  methane 
could  be  formed  synthetically.  This  conclusion  was 
severely  criticized  by  Bone  and  Coward2  on  the  ground 
that  the  low  temperature  experimental  range  would 
not  justify  such  wholesale  extrapolation.  This  ap- 
pears as  a  most  just  criticism.  Bone  and  Coward 
have,  in  fact,  converted  73  per  cent  of  a  quantity  of 

»  Ber.,  40  (1907),  2134-2144. 

2  J.  Chem.  Soc.,  93  (1908),  1975-1993,  and  97  (1910),  1219-1225. 

(18) 


pure  carbon  into  methane  at  noo°-i2oo°  by  passing 
hydrogen  over  it.  The  equilibrium  proportion  of 
methane  at  these  temperatures  is  exceedingly  minute, 
however. 

Earlier  work  done  by  Bone  and  Jerdan1  on  the 
synthesis  of  methane  at  1200°  C.  and  above,  has  been 
criticized  by  Berthelot,2  who  did  not  believe  that 
methane  could  be  synthesized  at  such  high  tem- 
perature, if  the  reaction  materials  were  pure.  Bone 
and  Coward's  results,  however,  appear  to  show  that 
this  is  not  true. 

Pring  and  Hutton3  obtained  o.io  to  0.25  per  cent 
methane  by  electrical  heating  of  purified  carbon 
rods  in  atmospheres  of  hydrogen  at  1250°  to  1350°  C. 
They  also  found  0.5  to  3.6  per  cent  acetylene  formed 
at  temperatures  between  1800°  and  2500°  C.  The 
amount  of  acetylene  increased  fairly  regularly  with 
the  temperature.  At  these  same  temperatures 
amounts  of  methane  ranging  from  o.  5  to  i.o  per  cent 
were  found  in  the  gases,  being  formed  no  doubt  largely 
by  the  decomposition  of  the  acetylene,  and  then 
moving  out  of  the  heated  zone  and  escaping  destruc- 
tion. 

Pring  and  Fairlie4  have  studied  the  methane  equi- 
librium. They  noted  that  at  temperatures  below 
1000°  C.  the  union  of  carbon  and  hydrogen  was  so 
slow,  even  with  application  of  pressure,  that  the 
equilibrium  proportions  could  not  be  reached  in  any 
reasonable  length  of  time.  Ethylene  began  to  be 
formed  at  1300°  C.,  and  the  quantity  in  equilibrium 
at  1400°  was  0.005  per  cent.  Acetylene  was  first 
•formed  at  1650°  C.,  and  the  amount  increased  with 
the  temperature  at  those  temperatures.  Where  ethyl- 
ene  and  acetylene  are  capable  of  formation  the  exact 
determination  of  the  methane  equilibrium  is  impossi- 
ble because  of  the  decomposition  of  these  gases  into 
methane.  The  amounts  of  methane  in  equilibrium 
are:  at  1200°  C.,  0.20  per  cent;  and  at  1500°  C.,  0.07 
per  cent. 

T.  Holgate6  pointed  out  that  the  curve  expressing 
the  rate  of  decomposition  of  methane  with  rise  of 
temperature  has  a  maximum  at  about  600°  C.  He 
believed  that  this  was  due  to  the  accumulation  of 
hydrogen  which  acted  as  a  brake  to  the  decomposi- 

'  J.  Chem.  Soc.,  71  (1897),  41-61. 
5  Ann.  chim.  phys.,  6    viii  (1905),   183. 
«  J.  Chem.  Soc.,  89  (1906),  1591-1601. 
4  Reports  8th  Internal.  Congress,  21,  65. 
*  J.  Gas  Lighting,  106  (1909).  25-28,  84-86. 

(19) 


tion.  Holgate  evidently  believed  that  the  reaction 
C  +  2H2  — >  CH4  had  an  appreciable  speed,  for  he 
said  that  above  607°  C.  "the  retarding  action  of  the 
square  of  the  hydrogen  pressure  is  greater  than  the 
effect  of  heat  in  driving  the  reaction,  and  as  a  result 
there  is  at  800°  C.  a  less  increase  in  the  rate  of  de- 
composition of  the  methane  per  degree  rise  in  tem- 
perature than  there  is  at  400°  C."  This  explana- 
tion is  not  in  accordance  with  the  various  investiga- 
tions of  the  methane  equilibrium  which  have  shown 
that  the  speed  of  the  reaction  C  +  2H2  — >  CH4  is 
inappreciable  at  temperatures  less  than  1000°  C. 

Ipatiew1  has  shown  that  even  in  the  presence  of 
the  catalysts  NiO  or  reduced  nickel,  which  have  proved 
most  effective  in  promoting  gaseous  reactions,  the 
union  of  carbon  and  hydrogen  could  not  be  detected 
at  650°  C. 

On  the  other  hand,  general  experience  shows  that 
at  temperatures  above  600°  C.  the  production  of  gases 
of  all  kinds  is  greatly  increased,  and  the  time  of  heat- 
ing of  the  gaseous  mixture  is  diminished  in  propor- 
tion to  this  increase  in  volume.  This  accounts  for 
the  fact  that  the  hydrocarbons  are  not  destroyed  be- 
fore leaving  the  coal  gas  retorts  of  the  water  gas 
superheater.  In  thinking  of  the  hydrocarbon  systems 
involved  here  it  must  be  kept  in  mind  that  the  reverse 
reactions  of  these  breaking  down  reactions  have  small 
velocities,  largely  on  account  of  the  removal  of  the 
end-products  of  the  decompositions  by  other  changes. 

It  can  be  seen  from  the  researches  cited  that  methane 
is  actually  tending  to  decompose  into  carbon  and 
hydrogen  at  the  temperatures  normally  operative  in 
water  gas  or  oil  gas  machines  or  coal  gas  retorts. 
That  this  decomposition  can  actually  be  brought  about 
on  a  large  scale  is  well  shown  by  the  work  of  Ostromiss- 
linski  and  Burshanadse,2  who  made  a  gas  containing 
75  to  80  per  cent  hydrogen  and  suitable  for  filling  bal- 
loons by  passing  hydrocarbon  gases  over  nickel,  nickel 
oxide,  or  oxides  of  iron. 

Brownlee  and  Uhlinger3  made  a  gas  containing 
90  to  95  per  cent  hydrogen  by  passing  natural  gas 
or  the  vapors  of  liquid  or  solid  hydrocarbons  over 
highly  heated  refractory  material. 

More  interesting  from  a  practical  or  working  point 
of  view  than  the  investigations  of  the  methane  equi- 

*  J.  prakt.  Chem.,  87  (1913),  479-487. 

2  J.  Russ.  Phys.-Chem.  Soc.,  42  (1910),  195-207. 

»  U.  S.  Pat.    1,168,931,  Jan.    18,    1916. 

(20) 


librium,  are  the  results  of  those  experiments  wherein 
the  working  conditions  approximate  those  of  actual 
practice. 

Simmersbach1  analyzed  coke  oven  gases  which  were 
heated  over  refractory  materials  for  10  to  14  seconds. 
The  proportion  of  methane  in  these  gases  at  800°  C. 
was  27.6  per  cent,  at  1000°  C.  20.  2,  at  1100°  C.  15.6, 
and  at  1200°  C.  5.  5  per  cent.  All  other  hydrocarbons 
disappeared  at  1000°  C.  The  stability  of  methane 
was  well  illustrated  here.  It  was  found  that  the 
decomposition  of  methane  was  practically  complete 
in  90  seconds  at  1000°  C. 

H.  Rollings  and  J.  W.  Cobb2  conducted  valuable 
experiments  on  the  stability  of  methane.  Mixtures 
of  methane  and  hydrogen  were  passed  through  an 
electrically  heated  tube.  At  800°  C.  with  a  mixture 
of  equal  parts  of  methane  and  hydrogen  it  was  found 
that  only  2  per  cent  of  the  methane  was  decom- 
posed on  passing  the  gases  when  the  time  of  heating 
was  one  minute.  At  1100°  C.,  65  per  cent  of  the 
methane  in  a  similar  mixture  was  decomposed  when 
the  duration  of  the  heating  was  47  seconds.  Thus 
methane  is  not  greatly  affected  at  800°  C.,  but  is 
rapidly  decomposed  at  1100°  C. 

The  work  of  Whitaker  and  Alexander3  showed 
that  methane  was  the  last  gas  to  be  decomposed  at 
temperatures  from  1400°  to  1600°  C.  With  oil  feed 
rates  of  10  cc.  per  minute  the  illuminants  disappeared 
at  1400°  C.,  whereas  3.  5  per  cent  of  methane  escaped 
destruction. 

Lewes4  passed  methane  through  a  platinum  tube, 
six  inches  of  which  was  heated  to  1000°  C.  Un- 
saturated  hydrocarbons,  to  the  extent  of  2.  7  per  cent, 
and  i .  8  per  cent  acetylene  formed.  He  concluded 
that  the  acetylene  was  formed  in  accordance  with 
the  reaction  2CH4  — >•  C2H2  +  3H2.  In  another 
paper  Lewes4  stated  that  methane  when  heated  to 
900°  C.  underwent  practically  no  change. 

Bone  and  Coward5  found  that  at  700°  C.  the  de- 
composition of  methane  was  inappreciable.  In  an 
experiment  at  785°  C.,  with  an  open  tube,  they  found 
that  91.6  per  cent  of  the  methane  used  was  unchanged 
at  the  end  of  one  hour,  the  rest  of  the  gas  being  hydro- 

>  Stahl  u.  Risen,  33  (1913),  239-45. 
*Gos  World.  60  (1914),  879-884. 
3  J.  Ind.  Eng.  Chem.,  1  (1915),  484-495. 

«  J.  Chem.  Soc.,  61  (1892),  322-338;  Proc.  Roy.  Soc.,  55  (1894),  90;  57 
(1895),  394. 

1J.  Chem.  Soc.,  93  (1908),   1197-1225. 

(21) 


gen.  Fjo  one  of  the  other  hydrocarbons  exhibited  any 
such  stability  at  these  temperatures.  Experiments 
were  conducted  at  1000°  and  at  1150°  C.,  from  the 
results  of  which  the  authors  concluded  that  the  nor- 
mal decomposition  of  methane  was  into  carbon  and 
hydrogen.  This  they  believed  to  be  a  surface  effect 
almost  exclusively.  Only  very  small  amounts  of 
acetylene  and  olefins  were  found  in  the  first  few  min- 
utes of  the  heating.  That  acetylene  or  olefins  were 
not  the  primary  products  of  the  decompositions  which 
then  undergo  decomposition  into  carbon  and  hydro- 
gen, Bone  and  Coward  believe  was  proved  by  the 
nature  of  the  carbon  deposit.  When  methane  decom- 
posed, the  carbon  was  of  a  peculiarly  hard  and  lustrous 
variety,  while  acetylene  and  ethylene  gave  a  soft 
dull  variety. 

In  summing  up  the  work  on  methane  it  can  be  said 
that  the  chief  reaction  is  the  decomposition  into 
carbon  and  hydrogen,  CH4  — >  C  -f-  2H2,  and  that 
the  reaction  suggested  by  Lewes  and  Berthelot, 
2CH4  — >  C2H2  +  3H2,  takes  place  to  a  small  ex- 
tent only. 

Under  the  conditions  of  operation  of  a  carbureted 
water  gas  set  very  little  methane  is  decomposed. 
Though  the  temperatures  of  the  retort  walls  in  coal 
gas  manufacture  are  much  higher  than  those  in  the 
interior  of  the  carbureter  and  superheater  of  a  water 
gas  set  it  is  obvious  that  the  gases  do  not  reach  the 
temperature  of  the  refractory  surfaces.  So  again 
methane  is  not  decomposed  to  a  large  extent. 

REACTIONS    OF    ETHANE 

H.  Rollings  and  J.  W.  Cobb1  passed  a  gas  of  the 
composition  4.2  per  cent  ethane,  47.5  methane, 
and  48.3  hydrogen  through  an  electrically  heated 
porcelain  tube.  At  800°  C.,  the  exit  gases  had  the 
composition  0.9  per  cent  ethane,  48.9  methane, 
48.9  hydrogen,  1.3  ethylene,  and  a  trace  of  acetylene. 
Thus  the  decomposition  of  ethane  took  place  to  an 
extent  of  79  per  cent  under  these  conditions  with  a 
time  of  heating  of  47  seconds.  At  1100°  C.  the  de- 
composition was  88  per  cent.  It  is  evident  that 
ethane  decomposes  to  ethylene,  methane,  and  hydro- 
gen. No  mention  was  made  of  the  separation  of  car- 
bon, but  on  the  other  hand  the  gases  passed  through 
a  tube  filled  with  coke  and  the  separation  of  carbon 
might  not  have  been  noticed. 

i  Gas  World.  60,  879-S84. 

(22) 


Lewes1  passed  ethane  through  a  platinum  tube, 
and  obtained  in  the  resulting  gases  19.5  per  cent 
unsaturated  hydrocarbons  and  8.  2  per  cent  acetylenes. 
When  ethane  diluted  with  80  per  cent  hydrogen 
was  heated  with  1 5  per  cent  air,  Lewes  found  7 .  7 
per  cent  unsaturated  hydrocarbons,  and  3.9  per  cent 
acetylenes.  He  believed  that  ethane  first  broke 
down  to  ethylene  and  hydrogen,  and  that  the  ethylene 
gave  rise  to  the  acetylene. 

Bone  and  Coward2  showed  that  the  primary  reac- 
tion which  ethane  underwent  when  heated  was  a 
dissociation  into  ethylene  and  hydrogen:  C2H6  <  > 
C2H4  -f  H2.  In  the  gases  from  the  decomposition 
of  ethane  they  found  the  ratio  of  the  methane  to  the 
hydrogen  to  be  about  2:1,  whereas  if  it  is  considered 
that  the  ethylene  formed  as  shown  in  the  equation 
above  decomposes  thus — C2H4  — >  CH4  -f  C — the 
ratio  of  methane  to  hydrogen  in  the  gaseous  products 
from  the  decomposition  of  ethane  should  be  i  :  i. 
This  can  be  explained  only  on  the  basis  of  the  assump- 
tion that  some  of  the  hydrogen  enters  into  combina- 
tion, forming  methane  or  products  which  by  their 
subsequent  decomposition  give  methane.  Bone  and 
Coward  suggested  that  it  was  due  to  the  hydrogena- 
tion  of  such  residues  as  — CH3,  =CH2,  =CH, 
which  can  be  thought  of  as  having  fugitive  existence. 
Their  results  in  this  connection  are  further  discussed 
under  our  caption  "  Atmospheres  of  Hydrogen." 

However,  "substances"  such  as  — CH3,  =CH2, 
and  =CH  are  in  a  class  with  ''nascent"  hydrogen.  The 
high  methane  content  of  these  resultant  gases  can 
be  explained  if  we  give  credence  to  the  possibility  of 
reactions  such  as  C2H6  +  H2  <  >  2CH4.  This  seems 
the  more  probable  when  we  call  to  mind  that  small 
amounts  of  acetylene  and  ethylene  are  found  in  the 
gases  which  result  from  the  heating  of  methane  as 
was  shown  by  Lewes.  The  acetylene  and  ethylene 
would  come  from  the  ethane  formed  as  in  the  equa- 
tion above,  v'" 

Bone  and  Coward  found  only  small  amounts  of 
acetylene  in  the  gases  from  the  decomposition  of 
ethane,  nor  did  the  formation  of  aromatic  hydrocar- 
bons take  place  to  a  large  extent.  At  800°  C.,  with 
one  minute  heating,,  only  17.9  per  cent  ethane  sur- 
vived. The  decomposition  of  ethane  was  not  be- 
lieved to  be  a  surface  effect. 

1  J.  Chem.  Soc.,  61  (1892),  322-338. 
*  Ibid.,  93  (1908).  1197-1225. 

(23) 


REACTIONS    OF    ETHYLENE 

Day,1  in  summing  up  the  work  of  Fourcroy,  De- 
Wilde,  Buff,  Hoffman,  Berthelot,  Marchand,  Grove, 
and  Magnus,  says:  "It  seems  clear  that  at  the  high- 
est temperatures  ethylene  separates  directly  into  its 
elements.  Below  this  point  marsh  gas  and  carbon 
are  obtained  (C2H4  — >  CH4  -f-  C),  then  marsh  gas 
and  several  liquid  products,  among  them  benzene, 
styrene,  etc.,  under  certain  conditions."  Day  circu- 
lated ethylene  through  a  glass  tube  heated  to  various 
temperatures  for  different  lengths  of  time.  No  change 
in  volume  was  observed  with  14  hours'  heating  at 
300°  C.  At  344°  C.,  a  contraction  of  one-twentieth 
of  the  original  volume  took  place  in  24  hours,  and  Day 
concluded  that  condensation  had  taken  place,  for 
no  methane  or  hydrogen  was  found  in  the  gas.  At 
400°  C.,  132  cc.  of  ethylene  contracted  to  63  cc.  in 
171  hours.  No  hydrogen  was  present  in  the  final 
gas,  which  was  a  mixture  of  22.4  cc.  methane,  24.8 
cc.  ethane,  and  15.6  cc.  ethylene  or  other  olefins. 

Norton  and  Noyes2  passed  ethylene  slowly  through 
a  glass  tube  heated  to  a  low  red  heat  for  60  cm.  of  its 
length.  The  products  passed  out  through  a  series 
of  U-tubes  immersed  in  a  freezing  mixture,  then  through 
ammoniacal  cuprous  chloride,  through  bromine,  and 
finally  to  a  gasometer.  Carbon  was  deposited  in 
the  tube.  From  the  liquid  condensing  in  the  freezing 
mixture  benzene  and  naphthalene  were  isolated.  Only 
traces  of  acetylene  were  in  the  gases,  and  the  authors 
concluded  that  if  acetylene  were  formed  it  must  have 
been  decomposed  in  the  tube.  The  liquid  bromides 
collected  consisted  chiefly  of  ethylene  dibromide, 
but  also  contained  some  methylene  dibromide,  propyl- 
ene  dibromide,  and  butylene  dibromide.  The  solid 
bromides  had  the  composition  C4H6Br4,  and  Norton 
and  Noyes  believed  that  it  could  be  explained  by 
the  reaction  2C2H4  — >•  C4H6  +  H2.  The  gases  col- 
lected consisted  of  methane  and  ethane. 

Sabatier  and  Sendefens3  passed  pure  dry  ethylene 
over  freshly  reduced  nickel  at  300°  C.  and  upwards. 
The  products  were  carbon,  hydrogen,  methane  and 
ethane  in  varying  proportions.  These  investigators 
found  that  the  hydrogen  increased  with  increase  in 
temperature,  and  believed  that  it  resulted  from  a 
secondary  reaction,  i.  e.,  decomposition  of  methane 

i  Am.  Chem.  J.,  8  (1886),  153-167. 

2/Wd.,  8  (1886),  362-364. 

»  Compt.  rend.,  124  (1897),  616-618. 

(24) 


into  carbon  and  hydrogen.  In  a  later  paper1  similar 
decompositions  were  carried  out  with  cobalt  as  the 
catalyst.  The  analysis  of  a  typical  gas  which  resulted 
was:  ethylene,  67.4;  ethane,  13.4;  methane,  4.4; 
and  hydrogen  14.8  per  cent.  As  would  be  expected, 
if  the  methane  equilibrium  is  kept  in  mind,  the  decom- 
position of  the  methane  in  the  presence  of  the  catalyst 
was  quite  extensive,  and  a  fairly  large  proportion  of 
the  hydrogen  so  formed  reacted  with  the  ethylene 
to  form  ethane. 

Bone  and  Wheeler,2  in  their  study  of  the  combus- 
tion of  ethylene,  found  that  when  insufficient  oxygen 
was  present .  to  burn  the  ethylene  to  formaldehyde 
a  thermal  decomposition  took  place.  The  products 
were  carbon,  hydrogen,  methane,  and  traces  of  acet- 
ylene. Ipatiew's  study  of  the  condensation  reactions 
of  the  ethylene  hydrocarbons  has  been  discussed  un- 
der the  secondary  decomposition,  but  should  be  called 
to  mind  again  here.  Engler  also  has  laid  emphasis 
on  the  importance  of  such  condensation  reactions. 

Pring  and  Fairlie3  found  that  small  amounts  of 
ethylene  were  formed  from  carbon  and  hydrogen; 
and  that  the  ethylene  so  formed  reacted  further  to 
give  methane. 

H.  Rollings  and  J.  W.  Cobb4  passed  a  gas  mixture 
containing  10.6  per  cent  ethylene,  47.7  methane, 
and  41.7  hydrogen  through  a  tube  heated  to  800°  C. 
The  exit  gases,  with  a  heating  time  of  45  seconds, 
contained  4.5  per  cent  ethylene,  54.4  methane,  40.3 
hydrogen  and  0.8  acetylene.  No  benzene  or  ethane 
were  found.  Methane  and  acetylene  appeared  to 
be  the  chief  products.  Apparently  the  reactions 
taking  place  were:  C2H4  — >•  CH4  +  C  and  C2H4  — > 
C2H2  +  H2.  The  first  of  these  was  much  the  most 
important  reaction.  A  contraction  in  volume  took 
place  which  the  authors  believed  was  due  to  the  forma- 
tion of  liquid  products.  At  1100°  C.  the  ethylene 
was  decomposed  completely  in  35  seconds'  heating. 

Lewes5  found  that  ethylene  yielded  considerable 
proportions  of  acetylene  when  it  was  decomposed 
by  heat.  From  a 'study  of  the  gases  made  from  Rus- 
sian oil  he  concluded  that  nothing  happened  till  a 

1  Compt.  rend.,  131,  iv  (1900),  267-270. 

2  J.  Chem.  Soc.,  85  (1904),   1637-1663. 

»  Repts.  8th  Int.  Congress  Applied  Chem.,  11,  65,  et  seq. 

*Gas   World,  60,   879-884. 

*  J.  Chem.  Soc.,  61  (1892).  322-338;  J.  Soc.  Chem.  Ind.,  11  (1892), 
584-590;  Proc.  Roy.  Soc.,  55  (1894),  90;  Trans.  Inc.  Inst.  of  Gas  Eng.,  10 
(1900),  111-133. 

(25) 


temperature  of  800°  C.  was  reached,  but  that  then 
the"  ethylene  began  to  decompose  in  accordance  with 
the  equation  3C2H4  — >  2C2H2  +  2CH4. 

The  experiments  of  Bone  and  Coward,  however, 
completely  disproved  any  such  mode  of  decomposi- 
tion for  ethylene.  From  their  work1  it  appeared 
that  ethylene  decomposed  in  different  ways  at  differ- 
ent temperatures.  In  the  study  of  the  thermal 
decomposition  of  ethane  at  675°  C.,  it  was  shown 
that  the  ethane  dissociated  first  into  ethylene  and 
hydrogen,  and  that  the  further  change  consisted  largely 
in  the  breaking  down  of  the  ethylene  into  carbon 
and  hydrogen.  When  the  reactions  undergone  by 
pure  ethylene  at  575°  C.  were  studied  it  was  found 
that  very  complex  gas  mixtures  were  obtained.  Acet- 
ylene, ethane,  methane,  hydrogen  and  aromatic  hydro- 
carbons were  all  present  in  notable  quantities  while 
the  separation  of  carbon  was  small.  The  experiments 
continued'  over  a  time  of  150  minutes  and  there  was  a 
continuous  decrease  in  the  volume  of  the  gases  which 
indicated  a  formation  of  aromatic  hydrocarbons. 

Bone  and  Coward  regarded  acetylene  as  one  of  the 
primary  decomposition  products  of  ethylene  at  the 
temperature  of  575°  C.  The  large  percentage  of 
hydrogen  without  a  corresponding  separation  of  car- 
bon precluded  Lewes'  contention  that  the  acetylene 
arose  largely  from  the  reaction  3C2H4  — >  2C2H2  + 
2CH4,  for,  were  this  the  main  reaction,  hydrogen  would 
result  from  the  secondary  decomposition  of  the  acet- 
ylene which  is  of  necessity  accompanied  by  separation 
of  carbon.  Experiments  were  conducted  at  700°,  800° 
and  950°  C.  The  higher  the  temperature  the  greater 
the  separation  of  carbon,  and  the  smaller  the  forma- 
tion of  aromatic  hydrocarbons.  Acetylene  and  ethane 
were  produced  in  smaller  amount,  but  methane  in 
larger  amount. 

Bone  and  Coward  have  some  difficulties  in  recon- 
ciling their  results  on  the  study  of  ethylene  alone, 
with  those  of  the  ethylene  resulting  from  the  dissocia- 
tion of  ethane.  The  formation  of  acetylene  is  much 
greater  and  the  decomposition  into  carbon  and  methane 
less  with  pure  ethylene  than  with  the  ethylene  result- 
ing from  the  decomposition  of  ethane.  It  seems  that 
the  presence  of  the  ethane  and  the  hydrogen  in  the 
latter  case  are  all-important. 

SUMMARY — It  appears  that  at  temperatures  up  to 
700°  C.  the  dissociation  of  ethylene  into  acetylene 

i  J.  Chem.  Soc..  93  (1908),  1197-1225. 
(26) 


and  hydrogen  is  the  most  important  reaction.  Con- 
densation also  takes  place  to  some  extent.  At  higher 
temperatures  the  rate  of  the  decomposition  into  car- 
bon and  methane  is  much  greater,  so  this  reaction 
plays  an  important  part.  The  high  proportion  of 
methane  found  by  Bone  and  Coward  at  temperatures 
of  about  800°  C.,  and  explained  by  them  as  due  to 
hydrogenation  of  unsaturated  residues  can  be  under- 
stood if  it  is  assumed  that  reactions  such  as 
C2H4  +  2H,  ^±1  2CH4  take  place. 

REACTIONS    OF    ACETYLENE 

It  has  been  seen  that  acetylene  is  formed  by  the 
dissociation  of  ethylene.  Many  authors  have  noted 
its  formation  in  the  gases  made  from  oil. 

Lewes1  has  shown  that  acetylene  was  present  in  the 
gases  made  from  Russian  petroleum  at  700°  to  1000° 
C.,  and  that  the  amount  increased  with  the  tempera- 
ture. The  percentages  were  0.084  at  700°,  0.38  at 
800°  and  0.46  at  900°  C. 

Haber  and  Oechelhauser2  claimed  to  have  found 
1. 10  per  cent  acetylene  in  gases  made  from  hexane 
at  temperatures  between  900°  and  1000°  C. 

Worstali  and  Burwell3  reported  1 1 . 8  per  cent  in 
the  gases  from  the  decomposition  of  heptane  and  oc- 
tane under  the  conditions  of  Pintsch  oil  gas  manufac- 
ture. The  presence  of  thte  amount  of  acetylene, 
however,  in  the  light  of  the  work  of  all  other  investiga- 
tors, is  open  to  confirmation;  e.  g.,  ammoniacal  cuprous 
chloride  was  used  to  absorb  the  acetylene  while  it  is 
known  that  this  reagent  will  absorb  ethylene  as  well. 

W.  A.  Noyes,  W.  M.  Blinks  and  A.  V.  H.  Morey* 
found  acetylene  in  the  oil  gases  made  at  900°  to  1000° 
C.  as  indicated  by  the  precipitate  obtained  when  the 
gases  were  passed  through  ammoniacal  cuprous 
chloride.  The  observation  of  these  investigators,  and 
many  more  which  might  be  mentioned,  rather  over- 
balance the  claim  of  Norton  and  Andrews5  that  they 
could  not  obtain  acetylene  in  the  gases  made  by 
passing  the  vapors  of  pentane  and  hexane  through  a 
porcelain  tube  heated  to  bright  red  heat.  It  is  ap- 
parent, therefore,-  that  the  reactions  of  acetylene 
are  of  some  moment  to  the  gas  manufacturer. 

1  J.  Soc.  Chem.  Ind..  11  (1892),  584-590. 

2  J.  Gasbel,  39  (1896),  377-382.  395-399,  435-439.  452-455.  799-805. 
813-818,   830-834. 

3  Am.  Chem.  J.,  19  (1897),  815-845. 

4  J.  Am.  Chem.  Soc.,  16  (1894),  688-697, 
4  Am.  Chem.  J.,  8  (1886),  1-9. 


R.  Meyer1  made  a  study  of  the  thermal  reactions 
of  acetylene.  If  the  gas  alone  was  passed  through  an 
electrically  heated  tube  at  650°  to  800°  C.  the  acet- 
ylene was  decomposed  into  carbon  and  hydrogen.  If 
hydrogen  was  mixed  with  the  acetylene  this  decom- 
position was  avoided.  The  gases  leaving  the  ap- 
paratus contained  some  methane.  The  tar  yields 
were  high,  in  one  case  60  per  cent  of  the  weight  of 
the  acetylene  used,  showing  the  decided  tendency 
of  acetylene  to  condense  to  higher  molecular  weight 
compounds.  Twenty  per  cent  of  the  tar,  by  weight, 
was  composed  of  benzene.  Naphthalene,  anthracene, 
indene,  toluene,  diphenyl,  fluorene,  pyrene  and  chry- 
sene  were  also  detected.  Meyer's  conclusion  was 
that  the  condensation  of  acetylene  was  an  essential, 
though  not  the  sole,  factor  in  the  formation  of  the 
aromatic  components  of  coal  tar. 

Not  all  investigators  have  agreed  that  benzene  is 
formed  from  acetylene. 

Norton  and  Noyes,2  in  their  experiments  on  eth- 
ylene,  found  only  small  amounts  of  acetylene  in  the 
g'ases,  and  yet  the  liquid  products  contained  fair 
amounts  of  benzene.  These  authors  said  that  if  ben- 
zene was  formed  from  acetylene  the  conditions  of 
their  experiments,  i.  e.,  low  red  heat,  must  have  been 
just  those  favorable  for  this  reaction  of  condensation. 

Lewes3  was  of  the  opinion  that  acetylene  when  heated, 
as  in  the  coal  gas  retorts,  condensed  at  once  to  ben- 
zene and  other  aromatic  hydrocarbons.  At  higher 
temperatures  it  was  decomposed  into  its  elements, 
and  this  according  to  Lewes,  was  the  only  reaction 
resulting  in  the  separation  of  carbon. 

.Berthelot4  had  previously  announced  similar  views. 
He  passed  acetylene  through  glass  tubes  at  low  tem- 
peratures and  obtained  solid  and  liquid  hydrocarbons 
among  which  were  benzene,  naphthalene,  and  styrene. 

Jacobson5  believed  that  acetylene  condensed  to 
benzene,  and  that  the  substituted  acetylenes  gave 
rise  to  toluene,  xylenes  and  mesitylene. 

Anschiitz6  pointed  out  that  if  it  was  considered 
that  a  hydrogen  molecule  split  out  the  formation  of 
naphthalene  could  be  accounted  for:  5C2H2  — > 
C10H8  +  H2. 

1  Ber.,   45   (1912),    1609-1633. 

2  Am.  Chem.  J .,  8  (1886).  362-364. 

»  Trans.  Inc.  Inst.   of  Gas  Engineers,   10   (1900).    111-113. 
4  Ann.  chim.  phys.,  9,  iv,  445,  469. 
*  Ber.,  10    (1877).  855. 
•Ibid.,  11  (1878),  1215. 

(28) 


Haber  found  that  benzene  and  some  naphthalene 
were  formed  by  passing  acetylene  through  a  tube 
at  700°  C. 

Sabatier  and  Senderens1  studied  the  action  of  the 
metals  copper,  nickel,  cobalt,  platinum,  and  iron  on 
acetylene.  At  temperatures  of  150°  to  250°  C.  a 
large  part  of  the  liquid  products  formed  were  aromatic 
hydrocarbons.  Decomposition  into  carbon  and  hydro- 
gen also  took  place,  and  nearly  all  the  hydrogen  so 
liberated  combined  with  the  acetylene  to  form  ethylene 
and  ethane. 

Bone  and  Coward2  showed  that  at  500°  C.  the 
principal  change  undergone  by  acetylene  was  condensa- 
tion, with  decomposition  into  its  elements  second 
in  importance,  while  hydrogenation  to  ethylene, 
ethane,  and  methane  was  least  important.  At  600°  C. 
the  relationship  was  found  to  be  much  the  same.  At 
800°  C.  the  gas  "flashed,"  and  the  temperature  locally 
was  much  higher  than  800°  C.  The  most  important 
feature  of  the  results  at  this  temperature  was  the 
higher  proportion  of  methane  in  the  resultant  gases. 
This  could  be  accounted  for,  according  to  Bone  and 
Coward,  only  by  assuming  the  hydrogenation  of  =CH 
residues  formed  momentarily  by  the  breaking  across 
a  triple  bond.  They  strengthened  this  argument 
by  heating  acetylene  in  nitrogen  and  hydrogen,  in 
the  ratio  of  C2H2  +  3N2  and  C2H2  +  3H2,  when  it 
was  found  that  five  times  as  much  methane  was  formed 
when  the  gas  was  cracked  in  hydrogen  as  when  the 
change  took  place  in  nitrogen.  Condensation  oc- 
curred at  800°  C.,  but  far  less  extensively  than  at 
lower  temperatures.  At  1100°  C.  condensation 
played  a  still  less  important  part,  decomposition  into 
the  elements  being  the  chief  change.  The  most  favor- 
able temperatures  for  the  condensation  of  acetylene 
lay  between  600°  and  700°  C. 

SUMMARY — It  would  appear,  then,  that  at  tem- 
peratures up  to  700°  C.  acetylene  undergoes  a  fairly 
rapid  condensation  to  benzene  and  its  homologs. 
Decomposition  into  carbon  and  hydrogen  is  second 
in  importance  at  these  temperatures  while  hydrogena- 
tion to  ethylene,  ethane  and  methane  is  least  important. 
At  slightly  higher  temperatures  the  importance  of 
condensation  diminishes,  while  the  decomposition 
into  the  elements  and  hydrogenation  both  increase. 
At  still  higher  temperatures,  such  as  1100°  C.,  the 

1  Compt.  rend.,  131,  iv  (1900),  267-270. 

2  7.  Chem.  Soc.,  93   (1908),   1197-1225. 

(29) 


decomposition   into   carbon   and   hydrogen   is   the   im- 
portant reaction. 

REACTIONS      OF      PROPYLENE,      DIOLEFINS,      SUBSTITUTED 
ACETYLENES,      PROPANE,      AND      HIGH      MOLECU- 
LAR   WEIGHT    TARRY    COMPOUNDS 

No  discussion  of  the  pyrogenic  reactions  of  pyro- 
pylene,  diolefins,  substituted  acetylenes,  propane,  and 
high  molecular  weight  tarry  compounds  was  found. 
A  few  conjectures  as  to  their  probable  reactions  may 
at  least  be  of  interest. 

PROPYLENE  can  condense  to  fo'rm  substituted  naph- 
thenes.  It  has  been  established  that  such  a  reaction 
does  take  place  in  the  case  of  ethylene,  and  it  is  en- 
tirely probable  that  propylene  undergoes  condensa- 
tion as  readily  or  more  readily  than  ethylene.  A 
rupture  of  the  propylene  molecule  with  formation 
of  acetylene  and  methane  is  also  not  an  improbable 
reaction,: 

CH3—  CH=CH2  — >  CH4  +  CH=CH 

The  DIOLEFIN  which  has  most  frequently  been 
isolated  and  identified  from  the  products  of  the  ther- 
mal decomposition  of  hydrocarbons  is  divinyl  or 
vinyl  ethylene,  CH2=CH— CH=CH2.  Whether  it 
is  formed  in  small  amount  only,  or  whether  it  is 
formed  in  large  amount  as  an  intermediate  product 
between  the  higher  olefins  and  more  complex  condensa- 
tion products  cannot  be  definitely  stated.  Isoprene, 
a  diolefin  of  the  supposed  formula  CH2=C(CH3) — 
CH=CH2,  is  known  to  condense  spontaneously 
to  dipentene,  and  ultimately  into  caoutchouc.  If 
judgment  from  analogy  is  allowable  it  would  seem 
that  divinyl  would  also  condense  readily.  This  rapid 
condensation,  rather  than  a  small  formation,  may 
be  responsible  for  the  fact  that  divinyl  is  found  in 
small  amount  only  in  the  products  of  hydrocarbon 
decomposition. 

It  may  be  regarded  as  well  established  that  acetylene 
will  condense  to  form  benzene  if  passed  through  a  tube 
heated  to  600°  to  750°  C.  So  it  would  be  probable 
that  the  substituted  acetylenes  would  undergo  similar 
reactions  with  formation  of  substituted  benzenes. 
That  such  reactions  actually  take  place  is  rendered 
the  more  plausible  by  the  observation  of  Rittman  and 
his  collaborators,  referred  to  under  the  discussion  of 
aromatic  hydrocarbons  in  this  paper,  that  the  sub- 
stituted benzenes,  such  as  cymene,  xylene,  and  toluene, 

(30) 


are  the  first  to  be  formed  when  paraffin  hydrocarbons 
are  decomposed  pyrogenically. 

PROPANE  may  easily  decompose  into  methane  and 
ethylene,  thus,  CH3CH2CH3  — >  CH4  +  CH2  =  CH2. 
This  reaction  is  analogous  to  the  primary  reaction  of 
the  higher  paraffin  hydrocarbons. 

The     HIGH     MOLECULAR     WEIGHT     TARRY     COMPOUNDS 

have  been  built  up  by  synthetic  reactions.  For  this 
reason  they  are  no  doubt  fairly  stable  compounds  as 
regards  the  influence  of  heat,  and  in  general  pass  on 
through  the  apparatus  and  into  the  tar.  Haber  has 
suggested  that  the  chief  reaction  of  the  compounds 
of  this  class  is  a  splitting  off  of  hydrogen. 

IV AROMATIC    HYDROCARBONS THEIR    FORMATION  AND 

REACTIONS 

Though  the  formation  of  aromatic  hydrocarbons 
takes  place  only  to  a  limited  extent  in  water  gas  ma- 
chines, and  to  but  a  slightly  greater  extent  in  coal  gas 
retorts,  the  tars  from  these  processes  are  important 
sources  of  the  commercial  aromatic  hydrocarbons. 

The  aromatic  hydrocarbons  contribute  greatly  to 
the  illuminating  value  of  a  gas  as  determined  in  an 
open  flame  burner.  However,  should  the  calorific 
standard  for  gas  service  in  the  course  of  time  become 
general,  the  presence  of  the  aromatic  compounds  in 
the  gas  would  be  of  far  less  importance  to  the  gas  manu- 
facturer than  it  is  to-day.  These  compounds  con- 
tribute less  to  the  heating  value  of  the  gas  than  the 
compounds  from  which  they  are  formed.  Their  chief 
importance  would  then  lie  in  the  better  prices  obtain- 
able for  the  tars  containing  them. 

Notwithstanding  these  facts  it  is  deemed  well  worth 
while  to  discuss  to  some  extent  the  literature  relevant 
to  the  formation  of  the  aromatic  hydrocarbons,  and 
the  changes  undergone  by  them. 

Lewes,1  in  commenting  on  Armstrong's  statement2 
that  benzene  was  not  formed  from  acetylene,  said 
that  he  believed  this  reaction  to  be  responsible  for  a 
part,  only,  of  the  benzene  formed  and  that  the  poly- 
methylene  hydrocarbons,  by  their  dissociation  into 
benzene  and  hydrogen,  contributed  largely.  The 
high  percentage  of  benzene  (20  per  cent)  in  Russian 
oil  tars  was  cited  as  proof. 

It  was  suggested  by  Armstrong  and  Miller3  that 
hexane  might  have  a  specific  tendency  to  condense 

1  J.  Soc.  Chem.  Ind.,  11  (1892),  584-590. 

2  Ibid.,  3   (1884),  462-468. 

1  J.  Chem.  Soc.,  49  (1886),   74-93. 

(31) 


to  hydro-aromatic  hydrocarbons  which  in  turn  would 
give  rise  to  benzene.  This  has  been  disproved  by 
Haber;1  approximately  equal  amounts  of  benzene 
were  found  in  the  reaction  products  of  hexane  and 
trimethylechylene.  The  latter  compound  could  not 
form  benzene  by  a  linking  together  of  the  ends  of  its 
carbon  chain. 

Considerable  recent  work  has  been  done  with  the 
commercial  production  of  aromatic  hydrocarbons 
as  its  object.  Though  these  investigations  have  not 
been  made  from  the  manufacturer's  gas  viewpoint, 
valuable  conclusions  as  to  the  mechanism  of  the  reac- 
tions of  the  aromatic  hydrocarbons  can  be  drawn 
from  them. 

Brooks  and  Humphreys2  discussed  the  presence 
of  aromatics  in  high  boiling  petroleum  distillates. 
Though  they  recognized  that  in  oil  gas  making  ben- 
zene no  doubt  results  from  the  polymerization  of 
acetylene  they  did  not  believe  that  such  condensa- 
tions were  responsible  for  the  benzene  in  their  distillates 
since  the  temperature  of  distillation  did  not  exceed 
420°  C. — at  which  temperatures  they  assumed  acet- 
ylene formation  negligible.  However  improbable  such 
formation  of  acetylene  may  be,  it  has  not  been  proved 
that  it  does  not  take  place.  These  authors  also  re- 
ferred to  the  work  of  Ogloblin,3  in  which  it  was  shown 
that  at  temperatures  of  525°  to  550°  C.,  Russian 
naphtha  (a  hydrocarbon  largely  composed  of  naph- 
thenes)  broke  down  readily  to  give  good  yields  of  ben- 
zene, toluene,  xylene,  and  smaller  amounts  of  naph- 
thalene and  anthracene.  Brooks  and  Humphreys 
referred  to  this  work  in  the  sense  that  the  tempera- 
tures of  525°  to  550°  C.  were  the  lower  limiting  tem- 
peratures at  which  these  reactions  would  take  place. 
Ogloblin,  however,  intended  to  convey  no  such  im- 
pression, and  stated  that  at  these  temperatures  the 
reactions  took  place  readily.  This  fact  convinces 
us  that  Brooks  and  Humphreys  were  in  no  sense 
justified  in  their  conclusion  that  the  benzene  in  their 
high  boiling  petroleum  distillates  arose  from  hydro- 
carbons containing  a  phenyl  radical. 

The  work  of  Engler  and  Lehmann4  can  be  mentioned 
in  this  connection.  These  investigators  found  naph- 
thenes  and  aromatic  hydrocarbons  in  oily  distillates 

1  J.  Gasbel,  39   (1886),  377-382,  395-399,  435-439,  452-455,  799-805, 
813-818,   8-30-834. 

2  J.  Am.  Chem.  Soc.,  38  (1916),  393-340. 

3  Z.  angew.  Chem.,  18  (1905),  540. 

4  Ber.,  30  (1897),  2365-2368. 

(32) 


made  by  heating  fats  under  pressure  at  temperatures 
below  those  used  by  Brooks  and  Humphreys. 

It  must  be  kept  in  mind  also  that  Rittman  and  his 
co-workers  have  obtained  maximum  yields  of  ben- 
zene at  temperatures  of  600°  C.  and  slightly  above 
and  4  atmospheres  pressure.  They  are  of  the  opinion 
that  condensation  of  acetylenes,  dehydrogenation  of 
naphthenes,  and  splitting  of  polycyclic  or  asphaltic 
hydrocarbons  all  contribute.  Egloff  and  Twomey1 
obtained  considerable  yields  of  benzene  at  450°  C. 
and  atmospheric  pressure. 

An  excellent  investigation  of  the  relationships 
between  the  most  important  aromatic  hydrocarbons 
has  been  made  by  Rittman,  Byron,  and  Egloff2  and 
by  Rittman  and  Egloff.3  They  used  the  pure  hydro- 
carbons cymene,  xylene,  toluene,  benzene,  naphthalene, 
and  anthracene,  which  were  treated  at  various  tem- 
peratures and  pressure  in  the  furnace  formerly  used 
by  Whitaker  and  Rittman.4  The  authors  came  to 
the  conclusion  that  from  cymene  it  was  possible  to 
produce  all  the  other  hydrocarbons  mentioned. 
Xylene  gave  toluene,  benzene,  naphthalene,  and 
anthracene,  but  no  cymene.  Toluene  gave  benzene, 
anthracene,  and  naphthalene,  but  no  cymene  or  xylene. 
Only  naphthalene  and  anthracene  may  be  produced 
from  benzene.  Naphthalene  yielded  anthracene  but 
none  of  the  others.  Anthracene  yielded  only  carbon 
and  gas.  The  authors  noted  that  other  compounds 
such  as  diphenyl,  methylnaphthalenes,  and  anthra- 
cenes, and  phenanthrene  were  formed  to  some  extent. 
It  can  be  seen  that  the  general  course  of  the  reac- 
tions with  monocyclic  aromatic  compounds  was  from 
higher  to  lower  molecular  weight  compounds,  and 
that  the  tendency  was  for  monocyclic  to  go  to  poly- 
cyclic  compounds. 

The  influence  of  various  conditions  on  the  formation 
of  aromatic  hydrocarbons  has  recently  been  reviewed 
by  Egloff  and  Twomey.5  This  paper  also  records 
the  results  of  an  investigation  of  the  effect  of  tempera- 
ture on  the  individual  aromatic  hydrocarbon  forma- 
tion at  atmospheric  pressure.  Temperatures  of  459° 
to  600°  C.  produced  more  toluene  and  xylene  than 
benzene  in  the  cracked  oil,  and  more  toluene  than 
xylene.  More  toluene  than  benzene  was  formed  at 

1  J.  Phys.  Chem.,  20  (1916),  121,  et  seq. 

2  J.  Ind.  Eng.  Chem.,  7  (1915),   1019,  et  seq. 

3  Met.  Chem.  Eng.,  14  (1916),   15-18. 

4  J.  Ind.  Eng.  Chem.,  6  (1914),  383,  472. 
*  J.  Phys.  Chem.,  20   (1916),    121-150. 

(33) 


650°  C.,  and  more  benzene  than  xylene.  No  naph- 
thalene or  anthracene  was  found  in  the  recovered 
oils  at  650°  C.  In  the  temperature  range  of  700°  to 
875°  C.  .more  benzene  was  formed  than  toluene  or 
xylene,  but  more  toluene  than  xylene.  At  750°  C. 
naphthalene  began  to  be  formed,  and  at  800°  C. 
anthracene  formation  commenced.  The  amounts  of 
both  of  these  hydrocarbons  increased  with  tempera- 
ture. The  authors  seemed  justified  in  their  conclu- 
sion that  the  individual  aromatic  formation  with  change 
of  temperature  was  as  follows: 

HIGHER  HOMOLOGs] 


,  TOLUENE 

such  as    mesity-  I 

,       ^     f     >  AND 

lene     pseudocu- 

XYLENE 

mene,  etc. 


BENZENE 


This  is  not  to  be  interpreted,  for  instance,  to  mean 
that  toluene  and  xylene  cannot  form  anthracene  or 
naphthalene  directly. 

THE  REACTIONS  or  BENZENE  have  been  the  subject 
of  a  number  of  investigations,  and  it  is  deemed  worth 
while  to  present  them  here  in  review.  Schultz1 
found  that  diphenyl  was  formed  by  passing  benzene 
vapors  through  tubes  heated  to  redness.  Meyer,2 
in  his  paper  on  the  condensations  of  acetylene,  noted 
the  presence  of  diphenyl  in  the  high  boiling  fractions 
of  the  liquid  obtained  by  passing  acetylene  through 
heated  tubes.  Ipatiew3  found  that  diphenyl  was  not 
formed  below  600°  C.  Smith  and  Lewcock4  passed 
benzene  vapors  through  a  heated  iron  tube  at  the  rate 
of  5  cc.  of  liquid  benzene  per  minute.  The  yield  of 
diphenyl  was  not  increased  by  the  use  of  tempera- 
tures above  720°  C.  The  time  factor  was  found  to 
be  important.  By  the  variance  of  conditions  yields 
of  diphenyl  ranging  from  o.o  to  59  per  cent  could  be 
obtained.  H.  Rollings  and  J.  W.  Cobb5  found  that 
the  decomposition  of  benzene  at  800°  C.  was  negligi- 
ble when  a  mixture  of  practically  equal  amounts  of 
methane  and  hydrogen  saturated  with  benzene  vapor 
was  passed  through  a  heated  tube.  At  1100°  C.,  no 
trace  of  the  benzene  could  be  found  in  the  products. 
According6  to  Haber,  benzene  was  not  decomposed  by 
heat  at  temperatures  below  900°  C.  Above  1000°  C., 

1  Ber.,  9  (1876),  547. 

2  Ibid.,  45  (1912),  1609-1633. 

3  J.  Russ.  Phys.  Chem.  Soc.,  39  (1907),  681. 
«  J.  Chem.  Soc.,  101  (1912),  1453-1458. 

s  Gas  World,  60  (1914),  879-884. 

•  J.  Gasbel,  39   (1896),  377-352,  395-399,  435-439,  452-455,  799-805. 
813-818,  830-834.  ' 

(34) 


however,  it  was  affected;  diphenyl  and  crystalline  sub- 
stances not  further  examined  were  found;  naphthalene 
was  not  observed. 

The  great  variation  in  the  results  of  these  authors 
shows  very  well  the  great  influence  of  conditions  on 
the  reactions  of  benzene.  Temperature,  pressure, 
and  time  of  heating  are  extremely  important. 

SUMMARY — The  reactions  responsible  for  the  aro- 
matic hydrocarbons  formed  in  the  pyrogenic  decom- 
position of  hydrocarbon  oils  are 

i — Condensation  of  acetylenes 
2 — Dehydrogenation  of  naphthenes 
3 — Decomposition  of  complex  compounds  already 
containing  the  phenyl  radical 

Toluene,  xylene,  ethyl  benzene,  and  similar  com- 
pounds are  formed  first  and  most  easily.  These  by 
further  change  give  rise  to  benzene,  naphthalene, 
and  anthracene.  With  high  molecular  weight  mono- 
cyclic  compounds  the  general  course  of  the  reaction 
is  toward  compounds  of  lower  molecular  weight.  In 
general,  monocyclic  compounds  tend  to  go  to  poly- 
cyclic  compounds. 

V INFLUENCE     OF     ATMOSPHERES     OF     HYDROGEN     AND 

INERT    GASES    ON    THE    PYROGENIC    DECOMPOSI- 
TION   OF    HYDROCARBONS 

The  idea  that  an  oil  cracked  in  hydrogen  or  in 
inert  gases  gave  more  valuable  products  has  been 
prevalent  for  many  years. 

Lewes1  states  that  the  better  results  are  obtained  by 
cracking  oil  in  gases  such  as  hydrogen,  carbon  mon- 
oxide, or  water  gas.  According  to  Lewes  these  gases 
exerted  their  helpful  influence  by  ' 'separating  and 
partly  protecting  the  molecules  during  the  decomposi- 
tion by  heat."  Thus  the  temperature  ranges  over 
which  good  results  could  be  obtained  was  increased, 
and  excessive  loss  and  breaking  down  of  the  hydrocar- 
bons prevented.  The  use  of  blue  water  gas  in  coal 
gas  retorts  was  also  advocated. 

Lewes2  found  a  considerable  increase  in  the  illumi- 
nants  formed  per  given  weight  of  Russian  oil  when  the 
oil  was  decomposed  in  atmospheres  of  inert  gases. 
He  also  commented  on  the  analogous  results  obtained 
by  the  use  of  the  Lowe  system,  and  was  of  the  opinion 
that  the  blue  water  gas  prevented  the  decomposition 
going  too  far,  and  also  aided  the  breaking  up  of  the 

1  Trans.  Inc.  Inst.  of  Gas  Engineers,  2  (1892),  77-85. 
.  2  J.  Soc.  Chem.  Ind.,  11  (1892),  584-590. 

(35) 


benzene.  Lewes  no  doubt  had  in  mind  the  fact  that 
dilution,  by  diminishing  the  partial  pressure  of  the 
acetylene,  would  tend  to  favor  the  acetylene  side  of 
the  equilibrium  3HC=CH  ^~±  C6H6. 

Numerous  patents  on  the  various  methods  of  using 
hydrogen  or  inert  gases  as  an  aid  to  the  decomposi- 
tion of  oils  have  been  issued.  The  patents  of  H. 
Blau1  are  illustrative:  these  involve  a  manufacture  of 
oil  gas  by  "expansion  and  rarefaction  with  permanent 
gases,"  whereby  the  separation  of  soot,  and  the  conse- 
quent irregularities  of  working  were  avoided. 

W.  Benthrup2  patented  a  process  for  the  introduc- 
tion of  water  gas  into  coal  gas  retorts  during  the  early 
stages  of  the  gasification.  The  gas  yield  was  supposedly 
increased,  and  a  better  quality  of  gas  obtained. 

H.  Croissant3  discussed  at  some  length  the  introduc- 
tion of  water  gas  into  coal  gas  retorts.  The  advan- 
tages according  to  him  are  the  increase  in  the  gas 
yield  from  the  coal,  and  a  gain  in  heating  value  of  7 
to  12  per  cent.  The  tar  was  more  fluid,  and  stoppages 
in  the  ascension  pipes  were  less  frequent.  Both  of 
these  latter  points  show  a  less  destructive  cracking 
of  the  hydrocarbons  distilled  from  the  coal.  The 
water  gas  should  be  introduced  in  the  proportion  of 
*/2  to  i  volume  for  every  2  volumes  of  coal  gas  during 
the  first  2  hours  of  the  period  of  carbonization. 

The  basis  of  the  Del  Monte  process  of  carboniza- 
tion4 developed  in  England  and  was  the  recirculation 
of  the  permanent  gases  (such  as  hydrogen  and  methane) 
through  the  coal  gas  retorts.  Excessive  cracking 
of  the  high  hydrocarbons  distilled  out  at  moderate 
temperatures  was  thus  prevented. 

Meyer's  work,  in  which  it  was  found  that  admix- 
ture of  hydrogen  with  acetylene  prevented  the  de- 
composition of  the  latter  into  carbon  and  hydrogen, 
has  already  been  mentioned. 

Several  other  authors  have  mentioned  the  effects 
of  decomposing  oils  in  water  gas.  Thus  C.  E.  Munroe 
stated  that  the  hydrogen  in  the  water  gas  had  the 
effect  of  increasing  the  olefins  and  diminishing  the 
amount  of  tar.  A.  E.  Forstall6  was  of  the  belief  that 
the  presence  of  water  gas  arrested  the  decomposition 

1  French  Pat.  332,115,  1903,  and  Ger.  Pat.  258,610,  1912. 

2  Ger.   Pat.    157,470,   1903. 

»  J.  Gasbel,  47  (1904),  219-222. 

*  Gas  World,  58  (1913),  321,  328,  430  and  477;  J.  Gas  Lighting.,  120 
(1913),  370. 

s  J.  Frank.  Inst.,  174  (1912),   1-33. 
•Ibid..    174    (1912),    279-302. 

(36) 


of  the  hydrocarbons  before  carbon  was  deposited, 
and  thus  allowed  the  use  of  a  larger  surface  of  contact 
for  heating.  Thomas  Holgate1  pointed  out  that  the 
curve  for  the  rate  of  decomposition  of  methane  with 
increase  of  temperature  had  a  maximum,  and  ascribed 
this  to  the  retarding  effect  of  the  increasing  amounts 
of  hydrogen  formed  by  the  decomposition. 

Redding2  cited  several  average  analyses  of  water 
gas.  These  are  shown  in  abbreviated  form  in  the 
following  table,  but  calculated  to  an  illuminants- 
carbon- monoxide- methane-hydrogen  basis. 

CARBON 

No.         ILLUMINANTS     METHANE       MONOXIDE  HYDROGEN 

1  10.4  19.9  33.6  36.1 

2  11.9  21.3  33.2  33.6 

3  14.5  14.0  35.1  36.4 

4  14.5  17.8  32.2  35.5 

Keeping  in  mind  that  the  water  gas  introduced  has  a 
little  more  hydrogen  than  carbon  monoxide  it  can  be 
seen  that  the  proportion  of  hydrogen  to  carbon  mon- 
oxide has  not  been  much  increased.  The  average 
analysis  of  Pintsch  gas  for  hydrogen  is  14  per  cent, 
but  evidently  the  oil  when  cracked  in  the  water  gas 
has  not  given  rise  to  this  amount  of  hydrogen.  This 
appears  as  good  evidence,  since  the  other  reactions 
which  might  tend  to  distort  the  carbon  monoxide- 
hydrogen  ratio,  namely,  2C  +  02  V**  2CO;  CO  -f 
HOH  ^±  CO2  +  H2;  and  CO2  +  C  ^±  2CO,  tend 
to  a  balance,  and  in  any  case  do  not  have  a  large 
effect. 

A  study  of  the  gasification  of  oils  in  hydrogen  and 
other  gases  was  made  by  Hempel.  In  his  experiments 
the  oil  was  gasified  and  led  into  a  i6-in.  tube  heated 
by  a  row  of  Bunsen  burners.  The  rate  of  gasifica- 
tion was  1.6  to  2.0  grams  of  oil  per  minute.  The 
gases  contained  from  30  to  36  per  cent  unsaturated 
hydrocarbons,  47.5  to  51  per  cent  saturated  hydro- 
carbons, and  14  to  17  per  cent  hydrogen.  The  prod- 
ucts of  decomposition  of  the  oil  and  the  hydrogen 
reacted  as  was  evidenced  by  the  15  per  cent  diminu- 
tion in  total  volume  when  the  hydrogen  was  introduced 
in  the  proportion  i  hydrogen  :  2  oil  gas.  The  resultant 
gases  were  practically  identical  with  those  produced  by 
cracking  oil  alone,  but  the  yields  of  methane,  ethylene, 
and  ethane,  according  to  Hempel,  were  increased  per 
unit  weight  of  oil.  The  ethane  particularly  was  in- 
creased. The  gases  showed  a  15  per  cent  gain  in  heat 
of  combustion  over  the  simple  oil  gases.  The  tars 

1  J.  Gas  Lighting,  106  (1909),  25-28,  84-86. 

2  Progressive  Age,  24  (1906),  485. 

(37) 


formed  were  more  fluid,  and  in  smaller  amount  by 
about  10  per  cent  when  the  oils  were  cracked  in  hydro- 
gen. The  separation  of  carbon  was  also  less  by  about 
1.5  to  3.0  per  cent.  The  experiments  indicated 
that  when  the  hydrogen  reached  a  proportion  of  50 
to  60  per  cent  of  the  final  gas  the  formation  of  gaseous 
hydrocarbons  was  confined  to  a  limited  quantity. 
When  hydrogen  was  used  in  the  proportion  of  i  hydro- 
gen :  i  oil  gas,  there  was  a  falling  off  in  the  produc- 
tion of  ethane  and  much  of  the  hydrogen  was  lost 
in  the  tars,  which  increased  in  amount.  The  most 
favorable  amount  of  hydrogen  is  about  18  cu.  ft. 
per  pound  of  oil.  The  opinion  was  expressed  that 
the  15  per  cent  hydrogen  normally  present  in  oil  gas 
exerts  a  considerable  influence.  From  a  very  limited 
investigation  Hempel  concluded  that  the  cracking 
of  oils  in  atmospheres  of  nitrogen  or  carbon  monoxide 
caused  no  change  in  the  volume  of  gas  produced  from 
the  oil,  nor  in  the  candle  power.  The  secondary  de- 
composition was  diminished  and  as  a  result  the  per- 
centage of  methane  falls  a  little  and  the  olefin  per- 
centage increases. 

E.  C.  Jones1  and  Z.  B.  Jones2  have  carried  out 
experiments  on  an  all-oil  water  gas  set  to  determine 
the  effect  of  the  cracking  of  oils  in  inert  gases,  and 
also  the  extent  to  which  carbon  monoxide  and  hydro- 
gen react  under  working  conditions  to  form  methane. 
They  established  that  the  inert  gases  had  the  effect 
of  increasing  the  proportion  of  carbon  in  the  gas  per 
unit  weight  of  the  oil,  and  in  their  technical  opera- 
tions cracked  the  oil  in  an  atmosphere  of  gas  from 
their  holder,  with  beneficial  effect.  Their  experi- 
ments showed,  too,  that  carbon  monoxide  and  hydro- 
gen united  to  some  extent  to  form  methane  and  water. 

Whitaker  and  Rittman3  noted  that  the  quantity 
and  quality  of  the  gas  formed  from  the  oil  increased 
when  the  oil  was  cracked  in  atmospheres  of  hydrogen, 
and  that  the  tar  and  deposited  carbon  decreased. 
They  found  that  more  hydrogen  entered  into  combina- 
tion with  the  decomposition  products  of  the  oil  at 
atmospheric  pressure  than  at  a  pressure  of  0.75 
pound  absolute. 

The  results  obtained  by  the  cracking  of  oil  in  atmos- 
spheres  of  hydrogen  may  be  ascribed  to  at  least  three 
factors : 

*  Am.  Gas  Lighting,  J .,  92  (1910),  437-445. 

2  Progressive  Age,  28   (1910).  373.  i 

»  J.  Ind.  Eng.  Chem.,  6   (1914),  472-479. 

(38) 


i- — The  dilution  effect,  which  is  the  same  as  diminish- 
ing the  partial  pressures  of  all  the  reacting  gaseous 
hydrocarbons. 

2 — The  increase  in  volume,  whereby  the  time  of 
heating  of  the  hydrocarbon  molecules  is  less  than  in 
the  making  of  straight  oil  gas. 

3 — Hydrogenation  of  hydrocarbons. 

The  first  of  these  factors  indicates  that  cracking 
oils  in  hydrogen  or  other  gases  should  favor  those  re- 
actions which  result  in  greater,  numbers  of  molecules: 
e.  g.,  the  tendency  of  acetylene  to  condense  to  ben- 
zene would  be  less  in  hydrogen  than  if  the  acetylene 
were  present  alone.  The  diminution  of  the  time  of 
heating  would  result  in  a  less  extensive  decomposi- 
tion of  the  various  hydrocarbons.  The  products  ob- 
tained should  be  those  of  the  earlier  stages  of  hydro- 
carbon decomposition  rather  than  the  large  amounts 
of  methane,  hydrogen,  and  aromatics  which  are 
obtained  by  very  extensive  changes.  The  extent  to 
which  hydrogenation  is  important  can  be  better  judged 
by  considering  the  experimental  work  which  bears 
directly  on  this  factor.  Some  mention  of  this  work 
has  been  made  under  our  discussion  of  the  secondary 
decomposition  of  hydrocarbons. 

P.  Sabatier  and  J.  B.  Senderens1  passed  acetylene 
and  hydrogen  over  various  catalysts  at  low  tempera- 
tures. With  cobalt  as  catalyst  there  was  formed 
26  per  cent  ethane,  70  hydrogen  and  4  of  a  mixture 
of  benzene  vapor  and  unchanged  acetylene.  Nickel 
as  catalyst  gave  even  more  ethane  than  cobalt,  while 
iron  was  far  less  active,  giving  chiefly  ethylene  and  its 
homologs. 

C.  Paal2  found  that  acetylene  was  easily  reduced 
to  ethylene  and  ethane  by  hydrogen  in  the  presence 
of  colloidal  palladium.  If  equal  volumes  of  acetylene 
and  hydrogen  are  taken  an  80  per  cent  yield  of  ethylene 
will  result. 

Ipatiew's  results3  on  the  hydrogenation  of  terpene 
hydrocarbons  and  aromatic  hydrocarbons  with  un- 
saturated  side  chain  should  also  be  mentioned.  Various 
catalytic  substances  were  used,  and  the  hydrogen  was 
introduced  under  100  to  no  atmospheres  pressure. 
The  hydrogenation  of  the  side  chain  took  place  at 
temperatures  of  95°  C.  in  the  presence  of  NiO  catalyzer^ 

1  Compt.  rend..  124  (1897),  832. 

2  Chem.  Zlg..  36  (1912),  60,  et.  seq. 

3  J.  Russ.  Phys.  Chem.  Soc..  43  (1911),   1754-1760;  45     (1913),    944- 
945;   45    (1913),    1829-1834. 

(39) 


while  the  aromatic  nucleus  was  hydrogenated  com- 
pletely only  at  temperatures  of  185  °  to  190°  C.  Though 
these  results  are  interesting  and  valuable  it  must 
not  be  concluded  from  them  that  similar  reactions 
would  take  place  when  these  substances  and  hydrogen 
are  heated  together  even  though  the  temperatures 
are  considerably  higher. 

Meyer1  in  his  study  of  the  pyrogenic  reactions  of 
acetylene  passed  mixtures  of  acetylene  and  hydrogen 
through  a  vertical  tutje  furnace  at  temperatures  of 
650°  to  800°  C.:  no  appreciable  formation  of  ethylene 
or  ethane  took  place.  Haber  found  i .  3  per  cent 
ethylene  in  the  gases  resulting  from  passing  a  mix- 
ture of  acetylene  and  hydrogen  through  a  tube  heated 
to  630°  to  645°  C.  Lewes  found  that  the  hydrogena- 
tion  of  acetylene  to  olefins  was  an  important  reac- 
tion at  1000°  C. 

The  noteworthy  results  of  Bone  and  Coward2  have 
already  been  mentioned  under  the  discussion  of  the 
decomposition  of  ethane.  To  further  validate  their 
explanation  of  the  high  ratios  of  methane  to  hydrogen 
these  authors  decomposed  mixtures  of  ethane  and 
nitrogen  in  the  proportion  of  i  ethane  :  3  nitrogen, 
and  ethane  and  hydrogen  in  the  proportion  i  ethane  : 
3  hydrogen  under  identical  conditions.  The  ratio  of 
methane  to  hydrogen  in  the  gases  from  the  methane 
nitrogen  mixture  had  the  approximate  value  of  unity, 
while  from  the  ethane-hydrogen  mixtures  it  was  much 
higher,  showing  a  considerable  hydrogenation  of  the 
decomposition  products  of  the  ethane;  2.27  times  as 
much  methane  was  formed  in  the  hydrogen  atmos- 
phere as  in  the  nitrogen  atmosphere.  Similar  ex- 
periments were  carried  out  with  ethylene  and  nitro- 
gen, and  ethylene  and  hydrogen.  The  results  ob- 
tained were  entirely  analogous  to  those  of  the  acet- 
ylene experiments.  The  ratio  of  the  methane  forma- 
tion in  the  hydrogen  atmosphere  to  that  in  the  nitro- 
gen atmosphere  was  3.15  :  i. 

Bone  and  Coward  have  shown  that  both  ethylene 
and  acetylene  have  a  certain  tendency  to  combine 
with  hydrogen  at  low  temperatures,  but  that  the  im- 
portance of  these  reactions  is  never  very  great,  and 
that  they  are  insignificant  above  1000°  C. 

In  so  far  as  the  work  of  these  several  investigators 
allows  us  to  draw  conclusions  it  seems  that  hydrogena- 
tion of  hydrocarbons  such  as  ethylene  and  acetylene 

i  Ber.,  45  (1912),  1609-1633. 

*  J.  Chem.  Soc.,  93  (1908).  1197-1225. 

(40) 


does  take  place,  but  that  it  is  never  a  reaction  of  great 
importance.  The  fact,  however,  that  hydrogen  is 
actually  absorbed  when  oils  are  cracked  in  atmospheres 
of  the  gas  shows  that  hydrogenation  of  some  sort  takes 
place.  Possibly  the  higher  unsaturated  hydrocar- 
bons are  hydrogenated  more  readily.  The  evidence 
from  our  experiments  in  this  connection  is  presented 
elsewhere  in  this  paper. 

VI TRANSFER  OF  HEAT  IN  GAS  MACHINES 

The  most  striking  feature  of  the  literature  which 
records  the  result  of  investigations  of  hydrocarbon 
decompositions  is  the  great  difference  between  the  re- 
sults of  various  investigators  who  report  that  they  have 
worked  at  the  same  temperature,  and,  in  general, 
under  the  same  conditions.  Irregularities  too  great 
to  be  attributed  to  the  personal  equation  are  of  fre- 
quent occurrence,  and  these  are  in  need  of  explana- 
tion. 

It  is  often  suggsted  that  these  differences  are  caused 
by  the  catalytic  effects  of  the  materials  of  construc- 
tion, but  without  doubt  the  catalytic  effect  of  contact 
surfaces  has  been  overestimated.  It  is  well  known 
from  general  experience  that  these  surfaces  are  always 
covered  with  a  layer  of  hard  carbon  as  a  result  of  the 
decomposition  of  hydrocarbons.  Hence  the  gases 
do  not  come  into  contact  with  an  active  material, 
but  rather  into  contact  with  a  dense  layer  of  carbon 
deposit  which  is  inactive  as  a  catalyzer. 

Unquestionably  many  of  the  effects  ascribed  to 
catalysis  are  in  reality  due  to  the  effectiveness  of  the 
heating  by  conduction  and  convection  close  to  the  sur- 
faces of  the  refractory  materials.  The  importance  of 
radiant  energy  in  causing  hydrocarbon  reactions  has 
also  been  overemphasized  most  consistently  in  the 
literature  of  the  gas  industry.  Too  little  attention 
has  been  paid  to  the  methods  of  making  temperature 
measurements,  and  also  to  the  interpretation  of  tem- 
perature measurements  made  in  certain  ways.  •  Thus 
it  is  obvious  that  a  metal  pyrod  with  a  metal  casing 
or  a  protective  sheath  of  solid  material  such  as  quartz 
will  absorb  many  times  as  much  radiant  energy  as 
the  gases  in  the  heated  space,  and  therefore  indicate 
a  temperature  considerably  above  the  true  tempera- 
ture of  the  gases.  Also  the  conduction  of  heat  along  the 
metal  pyrod  casing  is  more  effective  than  the  conduc- 
tion through  a  gas. 

The    processes    of    conduction    and    convection    are 

(41) 


FIG.   1 — Oil,  GAS  APPARATUS 
(42) 


.'Electrode  Holder 


- •  •  Cooling  Spray 

'Asbestos 

•A  sbestos  Disks 

"Carbon  Resistor 


Window 

---Carbon  side  Tube 
..'—  Carbon  Jacket  Tube 

. .  •  Petroleum  Coke 


'"•-  Pyrome 

Tube 


B 
FIG.  2 — RESISTANCE  FORNACB 

(43) 


dependent  on  the  extent  of  the  heated  surfaces  ex- 
posed to  the  gas,  and  the  manner  in  which  the  gases 
are  made  to  pass  over  these  surfaces.  The  heat 
transfer  from  the  hot  walls  of  the  retort  or  checker- 
brick  is  primarily  a  matter  of  heat  conduction  through 
a  thin  layer  of  gas  next  to  the  hot  surfaces,  and  second- 


To  0/li 
Tan) 


•  To  Pressure 
Gauge 


To  Oil  supply  Tank 


FIG.  3 — STATIC  HEAD  AND  FEED  REGULATOR 

arily  a  process  of  convection.  Conceived  of  in  terms 
of  the  kinetic  molecular  hypothesis,  the  molecules 
of  the  gas  very  close  to  the  hot  surfaces  can  be  thought 
of  as  striking  the  surfaces,  and  in  so  doing  having 
their  kinetic  molecular  energy  increased;  then  they 
dive  out  again  into  the  surface  layer  of  the  gas  where 

(44) 


by  numerous  impacts  the  newly  acquired  energy  is 
given  up  to  numbers  of  other  molecules.  The  mole- 
cules from  the  main  gas  stream  are  constantly  enter- 
ing the  surface  layer  and  those  in  the  surface  layer 
are  at  all  times  entering  the  gas  stream. 

In  addition  to  the  increase  in  the  kinetic  energy 
of  the  molecules  on  account  of  their  contact  with  the 
heated  bricks,  a  chemical  effect  must  no  doubt  be 
taken  into  account.  Langmuir1  has  explained  the 
abnormal^  heat  losses  from  lamp  filaments  glowing 
in  hydrogen  on  the  assumption  that  the  molecules 


Asbesfos 


Nichrome 
Wire  Heating 
Elements 


Asbestos 
packing  around 
Pipe 


m 


-  -Iron  Wire  Filling 
FIG.  4 — PREVAPORIZER 

of  the  gas^dissociate  into  atoms  with  absorption  of 
heat  near  the  filament,  and  that  the  atoms  then  diffuse 
away  from  the  wire  and  recombine  with  liberation 
of  the  heat  at  first  absorbed. 

Magnanini  and  Malagnini2  have  shown  that  the 
dissociation  of  a  gas  causes  an  abnormally  high  heat 
conductivity.  They  found  that  partially  dissociated 
nitrogen  tetroxide  had  three  times  as  great  a  heat 

1  Proc.  Am.  Electrochem.  Soc.,  20  (1911),  225-242. 

2  Nuovo  dm.,  6  (1892),  352. 

(45) 


conductivity  as  the  completely  dissociated  gas.  This: 
idea  can  readily  be  applied  to  the  transfer  of  heat 
in  gas  machines,  for  in  them  there  exists  a  complex 
gaseous  hydrocarbon  system  in  which  numerous 
endothermic  reactions  are  possible  in  the  highly  heated 
layer  close  to  the  checkerbrick  or  retort  surfaces. 
The  products  of  these  dissociations  then  diffuse  into 
the  outer  layers,  and  recombine  with  liberation  of 
the  heat  previously  absorbed,  thus  effecting  the 
heat  transfer. 

Lewes1  cites  experiments  by  Euchene  showing  that 
the  temperatures  of  the  gas  above  the  coal  in  a  re- 
tort varied  from  700°  C.  */2  hour  after  charging  to 
950°  C.,  4  hours  after  charging;  9  in.  of  space  were 
left  above  the  coal  in  the  retort  and  the  flue  tempera- 
ture was  approximately  1100°  C.  On  p.  144  Lewes 
states  that  in  a  horizontal  retort,  with  1100°  C.  flue 
temperature,  the  gases  left  the  mouthpiece  at  400°  C. 
during  the  first  few  hours  of  the  period  of  carboniza- 
tion and  then  dropped  100°  C.  during  the  last  2  hours. 
These  statements  appear  as  conflicting.  It  is  hard 
to  see  why  the  temperature  in  the  mouthpiece  of 
the  retort  should  not  vary  somewhat  with  the  tem- 
perature of  the  gases  in  the  retort.  Further,  it  is 
difficult  to  believe  that  gases  at  700°  to  950°  C.  could 
be  cooled  to  400°  C.  in  the  mouthpiece.  The  tempera- 
ture as  observed  in  the  mouthpiece  is  probably  more 
nearly  the  true  temperature  of  the  gases  in  that  part 
of  the  apparatus  than  the  temperatures  noted  in 
the  gas  space  above  the  coal  in  the  retort  are  for 
the  gases  filling  that  space. 

In  the  measurement  of  gas  temperatures  with  a. 
metal  pyrod  it  is  impossible  to  avoid  the  absorption 
of  radiations  from  the  solid  bodies  in  the  immediate 
vicinity.  This  would  no  doubt  play  an  important 
part  in  the  case  at  hand.  The  temperatures  recorded 
by  Euchene  are  in  all  probability  too  high  on  account 
of  the  absorption  of  radiant  energy  by  the  pyrod, 
whereas  this  energy  is  very  incompletely  absorbed 
by  the  gases.  This  difficulty  would  not  be  so  marked 
at  400°  C.  because  the  emission  of  radiations  of  this 
type  is  proportional  to  the  fourth  power  of  the  abso- 
lute temperature.  Hence  it  seems  not  improbable 
.that  the  temperatures  for  the  gas  above  the  coal  in 
the  retort  as  recorded  are  too  high.  However,  if 
the  gases  were  efficiently  absorbing  the  radiations. 

*  "Carbonization  of  Coal,"  pp.  132-133. 
(46) 


emitted  by  the  hot  walls  of  the  retort,  the  tempera- 
tures of  these  gases  would  be  at  least  as  high  as  those 
recorded  by  him.  Our  inference  is  that  this  radiant 
energy  is  not  absorbed  to  a  large  extent  by  the  gases, 
and  that  conduction  and  convection  play  far  more 
important  parts  in  the  heat  transfer  than  radiation. 

An  excellent  paper  by  Langmuir1  discusses  from 
a  theoretical  and  practical  point  of  view  the  heat 
transfer  by  means  of  radiation,  conduction  and  con- 
vection from  surfaces  of  various  shapes  into  air.  It 
is  interesting  to  note  that  the  air  near  a  hot  metal 
disk  was  heated  to  a  point  hot  enough  to  char  paper 
for  a  distance  of  only  l/4  in.  from  the  disk  even  when 
the  latter  was  heated  to  redness. 

Thus  in  the  superheater  and  carbureter  the  size 
of  the  voids  between  the  checkerbricks  must  be  very 
important  in  connection  with  the  results  to  be  ob- 
tained by  the  use  of  a  certain  temperature. 

Tyndall  and  Magnus  have  both  worked  on  the  dia- 
thermacy  of  gases  and  vapors.2  The  following  tables 
show  some  of  the  results  of  these  investigators. 

THE  WORK  OF  TYNDALL — In  these  experiments 
the  radiation  from  the  heat  source  passed  through  a 
column  of  gas  33  in.  long,  and  then  upon  a  thermopile 
used  to  measure  the  radiant  energy  passing  through 
the  gas.  The  source  of  the  radiant  energy  was  a 
copper  plate  heated  by  a  small  impinging  flame  from 
a  Bunsen  burner. 

EXPERIMENTS  AT  ATMOSPHERIC  PRESSURE 


SUBSTANCE 

%  Absorption 
of  Radiations         SUBSTANCE 
0  08         Hydrogen  sulfide 

%  Absorption 
of  Radiations 
31  0 

Nitrogen  

.  ..        0.08         Methane  

32.0 

Hydrogen 

0  08         Amylene  vapor 

60  3 

Carbon  monoxide  . 

.  .  .        7.1            Ethylene  

71.0 

Carbon  dioxide.  . 

7  .  1            Ammonia 

94.5 

Benzol  vapor  

...      21.2 

The   effect   of  pressure   is  shown   by  the   following 

data: 

PER  CENT  ABSORPTION 
SUBSTANCE  0 . 1  Atm.         0 . 5  Atm.          1 . 0  Atm. 

Benzene 5.25  14.5  21.2 

Amylene 13.2  39.2  60.3 

Thus  the  absorption  increases  with  the  pressure, 
but  not  in  direct  proportion  to  it,  nor  in  accordance 
with  any  simple  law. 

The  effect  of  temperature  of  the  source  of  the  radiant 
energy  can  be  seen  in  the  following  data:  The  figures 
are  not  per  cents  of  absorption  but  simply  numbers 

1  Proc.  Am.  Electrochem.  Soc.,  23  (1913).  299-332. 

2  Preston's  "Theory  of  Heat,"  p.  551-568. 

(47) 


representing  the  relative  absorptions  as  found  in  this 
particular  set  of  experiments. 

BARELY  BRIGHT  WHITE 

SUBSTANCE                 VISIBLE  RED            RED  HEAT 

Benzene...                   ...      26.3                   20.6  16.5 

Amylene 35.8                   27.5  22.7 

Thus  the  higher  the  temperature  the  less  the  ab- 
sorption of  radiant  energy  by  these  gases. 

MAGNUS'  EXPERIMENTS — The  source  of  the  radiant 
energy  in  Magnus'  experiments  was  at  the  tempera- 
ture of  boiling  water,  and  the  distance  through  the 
gas  traversed  by  the  radiations  was  15  in. 

SUBSTANCE  %  Absorption       SUBSTANCE  %  Absorption 

Vacuum 0.00          Methane 27.79 

Oxygen 11.12          Cyanogen 27.79 

Hydrogen 14.21          Ethylene 53.71 

Carbon  dioxide 19.77          Ammonia 61.12 

Carbon  monoxide 20 . 99 

These  results  are  considerably  lower  than  those  ob- 
tained by  Tyndall  in  the  case  of  the  hydrocarbon 
gases  and  ammonia,  but  higher  in  the  cases  of  oxygenr 
hydrogen,  carbon  dioxide,  and  carbon  monoxide. 
The  high  results  with  these  last-mentioned  gases  seem 
to  be  due  to  the  influence  of  convection  and  conduc- 
tion in  Magnus'  experiments. 

Langmuir  has  shown  that  out  of  a  total  heat  loss 
of  0.670  watt  per  sq.  cm.  for  a  vertical  oxidized  silver 
plate  0.134  watt  was  radiated,  and  0.536  watt 
were  conduction  and  convection  losses.  The  measure- 
ments were  made  in  still  air. 

Although  the  radiation  loss  would  be  greater  for  a 
body  under  black  body  conditions  such  as  exist  ap- 
proximately in  retorts  and  gas  machines  the  conduc- 
tion and  convection  losses  would  be  also  greatly  in 
creased  by  the  rapid  passage  of  the  gases.  Although 
no  data  are  available  on  this  question  it  seems  a  fair 
assumption  that  25  per  cent  of  the  heat  loss  from 
any  particular  checkerbrick  is  radiated  energy,  while 
the  rest  of  the  heat  is  transferred  by  conduction  and 
convection.  As  can  be  seen  from  the  data  of  Tyndall 
and  Magnus  cited  above,  ethylene  absorbs  more 
radiant  energy  than  any  of  the  other  gases  listed 
except  ammonia — the  absorption  lying  between  55 
and  77  per  cent  of  all  the  available  radiations.  But 
this  is  for  ethylene  at  i  atmosphere  pressure,  while 
the  partial  pressure  of  ethylene  in  a  water  gas  machine 
at  no  time  exceeds  o.  2  atmosphere.  Also  the  measure- 
ments of  Magnus  and  Tyndall  were  made  at  compara- 
tively low  temperatures  whereas  the  temperature 
in  the  gas  machine  is  in  the  neighborhood  of  700°  C. 

(48) 


The  absorption  of  radiations  by  gases  falls  off  with 
diminishing  pressure,  and  also  with  increasing  tem- 
perature. Taking  these  factors  into  consideration 
it  is  probable  that  not  more  than  one-quarter  of  the 
available  radiation  is  absorbed  by  the  ethylene.  On 
this  basis  only  one-sixteenth  of  the  total  heat  trans- 
fer from  the  checkerbricks  to  the  ethylene  is  due  to  ab- 
sorption of  radiant  energy.  In  the  cases  of  the  other 
gases  it  is  less  than  this.  For  hydrogen  it  is  almost 
negligible,  and  for  carbon  monoxide  very  small.  Al- 
though molecular  decomposition  would  not  be  expected 
in  the  cases  of  these  gases  at  these  temperatures,  the 
fact  that  they  are  not  effectively  atherrm'c  is  of  im- 
portance; for  did  they  absorb  radiations  to  a  large 
extent  they  would  then  transfer  the  heat  so  gained  by 
molecular  collision  to  the  hydrocarbon  molecules 
which  are  undergoing  important  molecular  changes, 
and  thus  influence  the  course  of  the  reactions. 

In  general  then,  it  would  seem  that  radiation 
does  not  play  as  important  a  part  in  transferring 
heat  as  has  been  taken  for  granted.  Conduction  and 
convection  are  largely  responsible  for  this  transfer, 
and  they  are  helped  to  some  extent  by  the  dissocia- 
tion reactions  of  the  hydrocarbons.  Catalysis  has 
been  greatly  overrated.  The  influence  on  reaction 
rates  supposedly  brought  about  in  this  fashion  can 
be  better  understood  if  the  true  mechanism  of  heat 
transfer  is  kept  in  mind.  The  different  results  of 
experimental  investigations  are  also  often  easily  un- 
derstood if  the  shape  and  size  of  the  apparatus  is  con- 
sidered in  its  relation  to  heat  transfer. 


(49) 


THE  DECOMPOSITION  OF  HYDROCARBONS  AND   THE 

INFLUENCE  OF  HYDROGEN  IN  CARBURETED 

WATER  GAS  MANUFACTURE 

H— EXPERIMENTAL 

Although  numerous  studies  of  hydrocarbon  de- 
composition have  been  made,  no  one,  nor  all  combined, 
comprise  a  complete  investigation. 

The  recent  work1  done  in  connection  with  the  com- 
mercial production  of  gasoline  and  aromatic  hydrocar- 
bons has  been  the  most  exhaustive  ever  attempted. 
However,  these  investigations  have  not  been  carried 
out  from  the  standpoint  of  gas  production. 

It  is  scarcely  necessary  to  discuss  the  importance 
of  a  thorough  understanding  of  the  possibilities  of 
controlling  the  decomposition  of  hydrocarbons  for 
the  obtaining  of  the  particular  products  desired. 

The  most  profitable  utilization  of  an  oil  is  of  extreme 
importance  to  the  water  gas  manufacturer.  The  con- 
trol of  the  cracking  of  an  oil  is  the  thing  of  first  im- 
portance to  the  manufacturer  of  oil  gas  in  any  of  the 
various  processes.  The  effect  of  the  presence  of 
hydrogen  on  the  products  derived  from  an  oil  is  of 
great  importance  to  the  water  gas  manufacturer  and 
the  all-oil-water-gas  maker. 

Also  it  is  generally  recognized  that  the  carboniza- 
tion of  coal  and  the  combustion  of  coal  and  oil  are 
allied  problems,  and  that  the  results  of  a  study  of  hydro- 
carbon decomposition  are  of  direct  application  in  these 
connections.  The  effect  of  the  introduction  of  hy- 
drogen into  the  carbonizing  retorts  can  also  be  seen 
by  a  study  of  the  data  given  in  this  paper. 

Brief  mention  of  the  experimental  work  of  a  few 
investigators  will  serve  to  show  the  importance  of 
the  subject  of  hydrocarbon  decomposition  to  the  users 
of  coal  for  gas  making  purposes  or  as  a  fuel. 

Jones  and  Wheeler2  have  extracted  solid  paraffins 
from  several  British  coals  by  means  of  pyridine  and 
chloroform.  Pictet  and  Ramseyer3  have  isolated 
hexahydrofluorene  from  that  portion  of  a  gas  coal 
which  was  soluble  in  benzene.  The  same  hydrocarbon 

1  Whitaker  and  associates  at  Columbia  University,  and  Rittman  and 
associates,  U.  S.  Bureau  of  Mines. 

*  J.  Chem.  Soc.,  103  (1913),  1704. 

»  Ber.,  44  (1911),  2486;  Gas  World,  56  (1911),  131. 

(51) 


has  been  identified  by  them  in  the  tar  obtained  by  the 
low  temperature  distillation  of  coal  in  a  vacuum. 
Burgess  and  Wheeler1  found  that  paraffin  hydrocar- 
bons were  predominant  among  the  primary  decomposi- 
tion products  of  coal.  The  same  authors2  found  a 
considerable  evolution  of  higher  olefins  when  coal 
was  distilled  at  low  .temperatures.  E.  Bornstein3 
discussed  the  decomposition  of  coal  at  temperatures 
up  to  450°  C.  He  found  that  the  gaseous  products 
consisted  of  5  to  14  per  cent  heavy  hydrocarbons,  55  to 
76  per  cent  paraffins,  and  5  to  16  per  cent  hydrogen. 
Jones  and  Wheeler4  distilled  coals  at  temperatures 
up  to  450°  C.  in  a  vacuum  of  5  to  40  mm.  of  mercury, 
and  obtained  6.5  per  cent  by  weight  of  a  tar  which  con- 
sisted of  25  per  cent  olefin  hydrocarbons  and  an  equal 
proportion  of  naphthenes  and  paraffins.  Pictet  and 
Bouvier5  have  conducted  experiments  similar  to  those 
of  Jones  and  Wheeler,  and  found  a  large  proportion 
of  hydroaromatic  or  naphthene  hydrocarbons  in  the 
tars.  Porter  and  Taylor6  found  that  the  primary  de- 
composition products  of  coal  were  complex  easily 
liquefiable  paraffins,  hydrocarbons  with  smaller  amounts 
of  water,  carbon  dioxide  and  hydrogen. 

One  of  the  points  in  the  propaganda  of  the  various 
recently  developed  low  temperature  carbonization 
schemes  has  been  the  high  percentage  of  light  hydro- 
carbon oils  which  might  be  recovered  from  the  tars 
and  used  for  motor  spirit.  The  gases  obtained  in 
these  processes  are  also  rich  in  higher  hydrocarbons. 
Lewes7  gives  the  analysis  of  a  gas  which  contained  10.1 
per  ce*nt  of  the  members  of  the  paraffin  series  higher 
than  methane. 

White,  Park,  and  Dunkerley8  found  the  ethane 
content  of  the  gases  of  low  temperature  carbonization 
processes  to  run  from  n  per  cent  to  47  per  cent. 
Parr  and  Olin9  have  found  that  approximately  10 
per  cent  of  a  light  hydrocarbon  oil  was  obtained  from 
tars  made  in  low  temperature  carbonization  experi- 
ments between  400  and  500°  C. 

1  J.  Chem.  Soc.,  99  (1911),  649-667. 
*lbid.,  105  (1914),  131-140. 

Z.  angew.  Chem.,  17  (1904),  1520. 

J.  Chem.  Soc.,  105  (1914),  140-151,  2562-2565. 

Compt.  rend.,  157  (1913).  779. 

Proc.  Am.  Gas  Inst.,  1914,  234-288. 

"Carbonization  of  Coal,"  p.  164. 

Proc.  Michigan  Gas  Assoc.,  17  (1908),  83. 

"Coking  of  Coal  at  Low  Temperatures,"  Bull.  79,   Univ.  of  Illinois 
Experiment  Station.  1915. 

(52) 


PURPOSE    OF    THE    PRESENT    INVESTIGATION 

It  is  the  purpose  of  this  investigation  in  general  to 
show  what  results  may  be  expected  in  the  decomposi- 
tion of  an  oil  if  temperature,  rate  of  oil  feed,  and  con- 
centration of  hydrogen  are  taken  into  account  and 
carefully  controlled.  More  specifically  it  is  proposed 
to  show: 

i — The  variation  of  the  composition  of  the  gases 
made  from  oil  at  constant  temperature  and  pressure 
with  changing  rate  of  oil  feed. 

2 — The  effect  o'f  changing  the  temperature  on  the 
composition  of  gases  made  from  oil  alone  at  constant 
oil  feed  and  constant  pressure. 

3 — The  variation  in  the  volume  of  the  various  gases 
obtained  per  cc.  of  oil  fed  at  constant  temperature  and 
pressure  but  with  changing  rate  of  oil  feed. 

4 — The  effect  of  changing  temperature  on  the  volume 
of  various  gases  obtained  per  cc.  of  oil  at  constant 
rate  of  oil  feed  and  constant  pressure. 

5 — The  extent  to  which  hydrogen  is  absorbed  at 
any  particular  concentration,  and  the  effect  of  changing 
the  concentration. 

6 — The  influence  of  hydrogen  of  certain  concentra- 
tion on  the  number  of  cc.  of  the  various  gaseous  com- 
ponents obtained  per  cc.  of  oil,  and  the  relations  be- 
tween this  and  change  of  concentration  of  hydrogen, 
change  of  temperature,  and  change  of  oil  rate. 

7 — The  results  of  a  study  of  the  mean  molecular 
weight  of  the  olefins  in  the  gases  at  certain  tempera- 
ture, and  the  influence  of  the  presence  of  hydrogen 
and  change  of  the  rate  of  oil  feed  in  this  connection. 

8 — The  proportion  of  aromatic  hydrocarbons  present 
in  the  gases  and  the  influence  of  the  presence  of  hydro- 
gen and  changing  oil  rate  in  this  connection. 

9 — The  percentages  of  tar  formed  at  different  tem- 
peratures and  rates  of  oil  feed,  and  the  influence  of 
hydrogen  on  tar  formation. 

PLAN    AND    SCOPE    OF    THE    EXPERIMENTAL    WORK 

The  plan  of  the  present  work  was  to  study  the  de- 
composition of  paraffin  hydrocarbons  under  atmos- 
pheric pressure,  and  at  a  number  of  temperatures  and 
varying  oil  rate;  and  under  identical  conditions,  to 
investigate  the  effect  of  the  presence  of  hydrogen  of 
different  concentrations  on  the  decompositions  of  the 
paraffin  hydrocarbons. 

The  working  temperatures  were  621°  C.,  723°  C. 
and  825°  C.  The  temperatures  used  in  the  commercial 

(53) 


manufacture  of  water  gas  lie  between  .700  and  775° 
C.,  and  are  thus  well  within  the  temperature  range  of 
these  experiments.  At  927°  C.  two  runs  were  made, 
but  the  separation  of  carbon  in  the  furnace  tube  was 
so  rapid  it  was  impossible  to  keep  the  tube  open  while 
the  adjustments  for  the  hydrogen-oil  gas  runs  were 
made.  The  hydrogen  concentrations  are  discussed 
under  the  caption  "The  Hydrogen  Concentration." 

The  method  used  was  to  adjust  the  furnace  to  the 
proper  conditions  and  to  run  the  oil  in  at  the  desired 
rate.  The  oil  gas  so  made  was  collected.  Without 
stopping  the  flow  of  oil,  hydrogen  was  then  admitted 
in  proper  concentration  and  the  gas  produced  by  crack- 
ing the  oil  in  hydrogen  collected  in  a  second  gasometer. 
The  two  gases  were  thus  made  under  identical  furnace 
conditions.  The  volumes  of  the  tars  formed  were 
measured. 

The  straight  oil  gas  runs  made  in  connection  with 
this  research  were  a  repetition  of  those  previously 
made  by  Dr.  C.  M.  Alexander  (private  communication), 
the  results  of  whose  work  have  not  as  yet  been  published. 
The  experimental  data  of  the  work  recorded  here  are 
in  excellent  agreement  with  those  of  Dr.  Alexander. 

APPARATUS  AND  PROCEDURE 

THE  FURNACE  used  in  these  experiments  was  designed 
and  built  by  Whitaker  and  Alexander,  and  used  by 
them  in  a  study  of  the  time  factor  in  the  making  of 
oil  gas.1  For  a  detailed  description  of  the  furnace  con- 
struction reference  must  be  had  to  the  original  article. 

The  heating  was  effected  by  the  passage  of  an  al- 
ternating current  from  a  single  phase,  60  cycle,  50  kilo- 
watt generator.  The  current  passed  through  the 
carbon  resistor  tube  of  the  furnace  was  readily  con- 
trolled by  means  of  a  field  rheostat.  Thus  a  very 
accurate  regulation  of  the  temperature  was  obtained. 
Fluctuation  limits  of  i  or  2°  C.  were  attained  by  care- 
ful operation. 

A  constant  feed  of  oil  was  readily  maintained  by 
means  of  the  static  head  and  feed  regulator.  The  oil 
was  vaporized  in  the  prevaporizer.  The  hydrogen 
gas  was  introduced  into  the  sight  feed  just  below  the 
oil  feed  valve  where  it  mixed  with  the  oil  vapors  com- 
ing from  the  prevaporizer,  and  passed  on  into  the  heated 
tube  of  the  furnace.  The  gas  velocity  in  the  tube 
could  be  calculated  from  its  dimensions  (i  in.  I.  D.  X 
38.5  in.  long),  and  the  total  gas  rate. 

i   J.  Ind.  Eng.  Chem..  7  (1915).  484-495. 

(54) 


Certain  features  of  the  design  of  the  furnace,  other 
than  the  fact  that  it  was  susceptible  to  exact  control, 
which  made  it  particularly  suitable  for  the  study  of 
the  reactions  of  hydrocarbon  decomposition  both  from 
a  theoretical  standpoint  and  from  an  operating  stand- 
point, must  be  pointed  out.  It  is  evident  that  the  gas 
in  passing  through  the  carbon  tube  is  subjected  to  a 
set  of  conditions  similar  to  those  existent  in  the  interior 
of  the  water  gas  carbureter  and  superheater;  i.  e., 
heated  by  carbon-coated  passageway  walls.  Though 
the  size  of  the  furnace  tube  is  less  than  the  voids  in 
the  checkerbricking  in  the  gas  machine,  the  general 
conditions  are  the  same. 

Both  from  a  theoretical  standpoint  and  practical 
standpoint  the  study  of  the  kinetics  of  these  various 
hydrocarbon  reactions  is  greatly  to  be  desired  as  has 
been  pointed  out  elsewhere  in  this  paper.  The  fur- 
nace was  designed  in  such  manner  as  to  avoid  catalytic 
effects  as  completely  as  possible,  and  is  therefore  suit- 
able for  a  study  of  the  kinetics  of  such  reactions. 

MEASUREMENT  OF  GAS  VOLUMES — The  gases  from 
the  runs  were  collected  in  5-cu.  ft.  holders.  The 
dimensions  of  these  tanks  were  carefully  taken  and  the 
volumes  computed.  A  stationary  millimeter  scale 
was  attached  to  the  tank  standard,  and  a  rigid  pointer 
to  the  movable  bell  so  that  readings  could  be  taken  at 
given  time  intervals,  and  the  gas  rates  and  total 
volumes  calculated. 

A  wet  meter  was  used  for  the  measurement  of  the 
volume  and  rate  of  the  hydrogen  flowing  into  the  ma- 
chine. This  meter  was  filled  with  kerosene  to  avoid 
the  aspiration  of  water  vapor  into  the  furnace.  The 
oil  level  in  the  meter  was  adjusted  carefully  at  all  times, 
and  the  meter  kept  perfectly  level.  The  meter  was 
calibrated  against  the  tank  which  was  used  for  the 
collection  of  the  mixed  oil-hydrogen  gases.  The  hy- 
drogen was  allowed  to  flow  into  the  meter,  through  the 
furnace  heated  to  800°  C.  and  into  the  receiving  tank, 
readings  being  taken,  at  short  intervals,  of  the  meter 
rate  and  tank  rate.  This  calibration  was  checked  from 
time  to  time  and  found  not  to  vary  appreciably. 

THE  PYROD  AND  ITS  CALIBRATION — The  temperature 
measurements  were  made  with  a  base  metal  thermo- 
couple attached  to  a  direct  reading  Wilson- Maeulen 
instrument.  The  thermocouple  was  calibrated  by 
checking  it  against  the  boiling  point  of  sulfur  (444.6° 
C.)  and  against  the  melting  point  of  sodium  chloride 
(800°  C.).  The  readings  of  the  thermocouple  at  these 

(55) 


points  were  425  and  775°  C.,  respectively.  Using 
these  data  a  curve  was  plotted  from  which  the  true 
temperature  could  be  read  corresponding  to  tempera- 
tures as  read  from  the  instrument. 

The  -temperatures  at  which  runs  were  made  were 
those  observed  when  the  pyrod  projected  through  a 
suitable  stuffing  box  into  the  lowest  of  the  sight  tubes. 
A  hole  the  size  of  the  end  of  the  pyrod  was  made  in 
the  carbon  resistor  tube,  and  the  pyrod  allowed  to 
project  about  l/*  in.  into  the  interior  of  the  resistor 
tube.  The  upper  portion  of  the  resistor  tube  was 
about  25-30°  C.  colder  than  that  part  of  the  tube 
where  the  pyrod  was  inserted,  due,  no  doubt,  to  the 
cooling  effect  of  the  incoming  gases  and  to  the  endo- 
thermic  reactions  taking  place  in  that  part  of  the  tube. 

THE  HYDROGEN  used  in  these  experiments  was  a  very 
high-grade  electrolytic  gas.  Analyses  showed  it  to 
contain  99.9  to  100.0  per  cent  hydrogen. 

THE  OIL  used  was  a  water-white  oil  (0.8000  sp. 
gr.),  which  boiled  between  150  and  265°  C. 

METHOD  OF  OPERATION — The  furnace  was  first 
heated  up  well  and  the  jacket  cooling  water  adjusted 
properly.  When  a  constant  temperature  10  to  30° 
above  the  temperature  at  which  the  run  was  to  be 
made  had  been  established,  the  oil  valve  was  opened 
and  adjusted  to  the  proper  rate  of  flow.  The  tem- 
perature of  the  furnace  was  then  regulated  till  it  re- 
mained constant  at  the  desired  point.  The  gases 
formed  during  this  preliminary  operation  were  run  to 
a  waste  tank,  and  the  tar  discarded. 

As  soon  as  all  the  proper  operating  conditions 
had  been  established,  the  gases  were  run  into  a  gas 
holder  and  readings  of  the  oil  rate,  gas  rate  and  tem- 
perature were  taken  at  suitable  short  intervals.  The 
pressure  was  always  atmospheric.  The  temperature 
was  noted  at  frequent  intervals,  and  any  necessary 
regulations  of  the  field  rheostat  were  made. 

When  the  proper  amount  of  gas  had  been  collected, 
the  gas  was  again  sent  to  the  waste  gas  holder,  and  the 
tar  removed  from  the  tar  drip.  Hydrogen  was  then 
admitted,  flowing  from  the  compressed  hydrogen  tank 
through  the  reducing  valve  and  meter  and  into  the 
admixer  at  the  top  of  the  furnace  tube.  When  the 
rate  of  the  hydrogen  flow  and  all  the  other  conditions 
had  been  adjusted,  the  gas  passing  was  run  into  a  sec- 
ond gas  holder.  Readings  of  the  oil  rate,  hydrogen 
rate,  total  gas  rate,  and  temperature  were  again  taken 
at  suitable  intervals. 

(56) 


Thus  an  oil  gas  and  a  hydrogen-oil  gas  were  made 
tinder  exactly  the  same  operating  conditions.  These 
gases  were  analyzed  18  to  20  hrs.  after  making. 
Analyses  were  made  on  low  temperature,  fast  oil  rate, 
gases  at  periods  of  one  to  two  hours  after  making  to 
see  if  the  standing  for  longer  periods  caused  any  differ- 
ence in  the  analytical  results.  No  appreciable  differ- 
ence was  found. 

RELATION     BETWEEN     THE     EXPERIMENTAL     APPARATUS 
AND    THE    COMMERCIAL    APPLIANCE 

Frequently  it  is  a  difficult  matter  to  reproduce  ex- 
perimental results  in  technical  operation.  It  is  with 
the  object  of  calling  attention  to  salient  points  which 
must  be  kept  in  mind  in  order  that  the  results  recorded 
here  may  be  reproduced  in  a  commercial  appliance  that 
the  paragraphs  which  follow  are  written. 

Experimental  results  show  that  the  time  factor  is  all 
important.  But  it  must  be  remembered  that  the  fur- 
nace tube  used  in  these  experiments  was  only  30  in. 
long,  whereas  the  column  of  checkerbrick  in  the  car- 
bureter and  superheater  of  the  water  gas  set  is  many 
times  that  length.  Hence  even  though  a  pyrometer 
may  record  the  same  temperature  in  this  furnace  and 
in  the  checkerbrick  of  a  commercial  machine  it  would 
not  be  expected  that  the  gases  would  have  the  same 
composition. 

The  diameter  of  the  furnace  tube  used  in  these  ex- 
periments was  i  in.  This,  however,  was  soon  car- 
bonized so  that  it  was  more  nearly  3/4  in.  The  inter- 
stices in  the  checkering  of  commercial  machines  are 
of  greater  sectional  area  than  a  circle  of  3/4  in.  diameter. 
Hence  the  opportunity  for  heat  transfer  in  the  checker- 
brick  is  not  so  good  as  in  this  experimental  furnace  and 
it  would  be  expected  that  a  longer  column  of  checker- 
brick  than  was  necessary  in  this  furnace  would  be 
necessary  to  produce  a  given  result,  all  conditions  being 
the  same. 

The  actual  time  of  contact  of  the  gases  with  heated 
surfaces  is  all  important,  but  it  is  a  very  complicated 
function  of  the  rate  of  oil  feed,  the  amount  of  blue 
gas  introduced,  the  volume  of  the  checkerbrick  voids, 
and  the  temperature. 

Commercial  operation  demands  that  an  apparatus 
have  a  reasonable  gas  making  capacity,  and  for  this 
reason  the  higher  oil  rates  are  most  desirable.  On  the 
other  hand,  with  high  oil  rates  more  tar  is  always 
produced  than  at  low  oil  rates,  which  makes  the  use  of 

(57) 


the  oil  uneconomical.  It  is  not  improbable  that  the 
best  results  could  be  obtained  by  designing  one  ap- 
paratus with  proper  control  suitable  to  the  production 
of  certain  gaseous  products,  and  a  second  apparatus 
which  would  use  the  tar  from  this  first  machine  as  the 
carbureting  oil.  An  examination  of  the  tars  formed 
in  the  experimental  apparatus  at  medium  to  high  rates 
of  oil  feed  have  led  to  the  belief  that  this  would  not  be 
impracticable. 

Methods  of  temperature  measurement  must  not  be 
neglected.  Above  all  it  must  not  be  assumed  that 
a  particular  temperature  as  measured  will  produce 
the  same  results  in  two  different  machines. 

The  experiments  recorded  in  this  paper  merely 
show  the  possibilities  in  the  decomposition  of  a  hydro- 
carbon oil.  To  obtain  particular  results  on  a  commer- 
cial scale  would  necessitate  a  great  deal  of  thought  as 
to  the  proper  design  for  the  machine  to  be  used. 

THE    HYDROGEN    CONCENTRATION 

The  introduction  of  hydrogen  in  certain  concentra- 
tion is  a  question  which  must  be  regarded  from  at 
least  two  standpoints;  i.  e.,  the  experimental  and 
the  technical  or  operating  standpoints. 

In  the  manufacture  of  carbureted  water  gas  the 
oil  is  cracked  in  an  atmosphere  of  carbon  monoxide 
and  hydrogen.  The  final  gas  is  roughly  1/3  hydro- 
carbons, 1/3  hydrogen  and  1/3  carbon  monoxide.  The 
hydrogen  and  hydrocarbons  are  thus  present  in  the 
approximate  ratio  of  i  volume  to  i  volume  in  the  final 
gas.  In  addition  there  is  present  i  volume  of  carbon 
monoxide,  the  influence  of  which  has  never  been  ex- 
actly determined  by  a  comprehensive  study. 

In  these  experiments  it  was  thought  desirable  to 
study  two  concentrations  of  hydrogen: 

(i) —  i  Volume  Hydrogen  :  2  Volumes  (oil  gas  +  tar  gas) 
(2) —  2  Volumes  Hydrogen  :  i  Volume  (oil  gas  +  tar  gas) 

The  experimental  difficulties  were  such,  however, 
that  the  introduction  of  hydrogen  in  exactly  these  pro- 
portions was  practically  impossible,  for,  with  change 
in  temperature,  the  amount  of  gas  produced  from  a 
given  quantity  of  oil  at  a  particular  rate  changes, 
while  with  change  in  oil  rate  at  constant  temperature 
the  amount  of  gas  produced  from  a  given  quantity 
of  oil  changes.  Also  the  gas  formed  from  a  certain 
amount  of  oil  is  different  when  the  oil  is  decomposed 
alone  or  in  an  atmosphere  of  hydrogen.  Furthermore, 
the  concentration  of  hydrogen  in  the  upper  part  of  the 

(58) 


furnace  tube  is  much  greater  at  any  time  than  it  is  in 
the  lower  part  of  the  tube,  for  as  the  oil  vapors  pass 
through  the  tube  a  progressive  decomposition  takes 
place  with  formation  of  a  greater  volume  of  hydro- 
carbon gases. 

It  would  therefore  be  necessary  to  make  several  trial 
runs  at  each  oil  rate  at  each  temperature  to  determine 
the  proper  hydrogen  rate.  When  it  is  considered  that 
each  run  of  that  sort  would  consume  several  hours' 
time,  the  impracticability  of  this  method  of  procedure 
is  apparent.  Furthermore,  in  commercial  operation 
the  two  factors  which  would  be  susceptible  to  control 
would  be  the  rate  of  introduction  of  blue  gas  and  the 
rate  of  introduction  of  the-  oil.  So  it  was  decided 
to  base  the  hydrogen  concentration  arbitrarily  on  the 
oil  rate.  After  some  trials  at  723°  C.,  the  following 
equations  relating  to  the  hydrogen  rate  and  the  oil  rate 
were  decided  upon: 
(/)  To  approximate  i  Vol.  Hydrogen  :  2  Vols.  (oil  gas  +  tar  gas) 

Oil  rate  in  cc.  per  minute  _  $  Hydrogen    rate     in     liters 

5.28  I  per  minute. 

(2)     To  approximate  2  Vols.  Hydrogen  :  i  Vol.  (oil  gas  +  tar  gas) 

Oil  rate  in  cc.  per  minute   _  \  Hydrogen    rate    in    liters 
i~;6 ~  )  per  minute. 

One  set  of  runs  only  was  made  at  621°  C.  and  this 
at  the  supposed  ratio  /  Vol.  Hydrogen  :  2  Vols.  Gas. 
The  lower  curve  in  Fi'g.  5  is  plotted  from  the 
equation  given  under  (i)  above.  The  points  repre- 
sent the  actual  hydrogen  rates  and  show  how  closely 
it  was  possible  to  adjust  the  hydrogen  rate  to  that  de- 
sired as  calculated  from  the  oil  rate. 

The  upper  curve  in  Fig.  5  shows  the  actual  ratio  of 
hydrogen  to  (oil  gas  +  tar  gas).  In  the  furnace  the 
hydrocarbons  which  compose  the  tar  are  of  course 
gaseous  and  the  volume  of  this  gas  is  calculated  on  the 
assumption  that  the  specific  gravities  of  the  liquid  tars 
are  0.80  (water  =  i)  and  that  the  mean  molecular 
weight  of  the  hydrocarbons  contained  in  the  tar  is 
142;  i.  e.,  that  the  average  molecule  contains  10  carbon 
atoms. 

The  straight  line  'at  ordinate  0.5  is  the  theoretical 
curve  for  the  value  of  the  ratio  of  hydrogen  to  (oil 
gas  -f  tar  gas).  It  can  be  seen  that  the  value  of  this 
ratio  more  nearly  approximated  unity  than  it  did  0.5 
in  these  runs. 

A  second  series  of  runs  with  the  value  2  for  the  ratio 
of  hydrogen  to  (oil  gas  +  tar  gas),  was  not  made  for 

(59) 


f    30 


.30 


-20 


10 


Point 
"Y 


G. 


Ro. 


J 


Oil    Rate  -  cc.   per    minute 


FIG. 


Oil  Rate  -  cc.  per   minute. 


Point 


Hydroqen 


Actua 


JO         3S        40 

Oil     Rate   -  cc.   per     minute   -    — - 

EFFECT  OF  DIFFERENT  HYDROGEN  CONCENTRATIONS  WITH  VARYING  Om 

RATES  AT  THREE  TEMPERATURES 
Data  for  Curves  Calculated  on  Two  Bases 

(60) 


the  reason  that  from  the  results  at  higher  temperatures 
it  was  judged  that  the  chief  effect  of  more  hydrogen  at 
621  °  C.  would  be  to  blow  the  vapors  through  the  heated 
tube  faster  without  producing  extensive  chemical 
change.  Since  there  was  approximately  i  volume 
of  hydrogen  to  i  volume  of  (oil  gas  +  tar  gas),  in  these 
runs  at  621°  C.,  that  is,  practically  the  relations 
existent  in  the  carbureter  and  superheater  of  the  water 
gas  set,  it  was  thought  that  this  series  of  runs  sufficed 
to  show  the  possibilities  of  a  temperature  in  the  neigh- 
borhood of  621°  C.  for  purposes  of  gas  manufacture. 

Curves  A  in  Figs.  6  and  7  are  the  plots  of  the  equa- 
tion under  (2)  given  above  at  723  and  825°  C., 
respectively,  and  curves  B  in  Figs.  6  and  7  the  plots 
of  equation  (i)  above  at  those  temperatures.  The 
points  show  how  closely  the  actual  hydrogen  rates 
approximated  those  calculated  by  these  equations. 

The  lower  curve  in  the  upper  half  of  Fig.  6  shows  that 
the  actual  value  of  the  ratio  of  hydrogen  to  (oil  gas  + 
tar  gas)  approximated  very  closely  to  the  value  0.5 
drawn  horizontally  on  the  ordinate  0.5.  The  upper 
curve  in  the  upper  half  of  Fig.  6  shows  that  at  low  oil 
rates  too  little  hydrogen  was  introduced  to  make  the 
value  of  the  ratio  hydrogen  to  (oil  gas  +  tar  gas) 
equal  to  2.0,  and  at  high  oil  rates  that  too  much  hy- 
drogen was  introduced. 

The  actual  values  of  the  ratio  hydrogen  to  (oil  gas 
4-  tar  gas)  in  the  second  series  of  runs  at  825°  C.  are 
shown  in  the  curves  in  the  upper  half  of  Fig.  7.  In 
the  first  series  of  runs  the  value  of  the  ratio  lies  be- 
tween i.o  and  2.0,  whereas  it  was  intended  that  it 
should  be  2.0.  In  the  second  series  the  desired  value 
0.5  is  very  closely  approximated  at  all  oil  rates. 

ANALYTICAL  PROCEDURE  FOR  GASES 

During  the  early  part  of  the  work  recorded  in  this 
paper  the  method  of  gas  analysis  was  the  ordinary 
one  employing  the  Hempel  burette  with  single  and 
double  pipettes  for  the  absorbing  reagents.  Thus 
the  carbon  dioxide  was  removed  by  a  solution  of  i 
part  of  KOH  in  2  parts  of  water,  the  unsaturated 
and  aromatic  hydrocarbons  by  fuming  sulfuric  acid 
with  20  per  cent  free  SO3,  the  oxygen  by  alkaline 
pyrogallol  made  up  in  accordance  with  HempePs 
directions,1  and  the  carbon  monoxide  absorption  in 
ammoniacal  cuprous  chloride  prepared  according  to 
Winkler.2  A  portion  of  the  residual  gas  was  then  mixed 

1  Dennis'  "Gas  Analysis,"  p.  160. 

2  C.  Winkler,  "Handbook  Tech.  Gas  Anal.,"  translated  by  Lunge,  p.  73. 

(60 


with  oxygen,  and  slowly  passed  back  and  forth  over 
palladium  black  in  a  glass  tube  immersed  in  water  at 
a  temperature  of  about  85-90°  C.  After  thus  re- 
moving the  hydrogen  the  gas  mixture  was  exploded 
over  mercury,  and  the  resulting  carbon  dioxide  ab- 
sorbed in  potassium  hydroxide. 

"CARBON  MONOXIDE" — As  the  work  progressed  it 
became  evident  that  this  method  could  be  improved 
upon.  It  was  difficult  to  understand  where  the  carbon 
monoxide,  varying  from  0.2  per  cent  to  1.9  per  cent 
as  shown  by  the  cuprous  chloride  absorption,  could 
have  come  from.  The  furnace  was  tight,  and  in  any 
case  there  would  be  a  slight  positive  pressure  out- 
wards, so  that  the  ingress  of  air  in  more  than  small 
amounts  was  out  of  the  ques.tion.  The  only  other 
possible  source  of  oxygen  was  the  water  in  the  oil 
used.  However,  had  the  carbon  monoxide  arisen 
thus  from  the  reaction  of  steam  on  the  carbon  it  would 
have  been  present  in  larger  amount  at  800°  C.  than 
at  600°  C.  Also  there  should  have  been  some  re- 
lation between  the  percentages  of  carbon  monoxide 
and  carbon  dioxide.  But  carbon  monoxide,  as  indi- 
cated by  the  absorption  in  ammoniacal  cuprous 
chloride,  was  present  in  largest  amount  at  600°  C.,  in 
smaller  amounts  at  700°  C.,  and  least  of  all  at  800° 
C.  Also  it  was  noticed  that  at  any  particular  tem- 
perature the  carbon  monoxide  tended  to  be  highest 
when  the  oil  rate  was  highest.  However,  there  was 
no  regular  variation  of  this  sort  as  there  was  with  the 
other  components  of  the  gaseous  mixtures  formed. 
Hence  it  appeared  that  the  "carbon  monoxide"  forma- 
tion as  shown  by.  the  absorption  in  the  ammoniacal 
cuprous  chloride  was  not  solely  a  function  of  the  furnace 
conditions. 

F.  C.  Phillips1  stated  that  cuprous  chloride  solu- 
tion dissolved  the  higher  members  of  the  paraffin 
series  to  some  extent.  G.  A.  Burrell  and  F.  M.  Seibert2 
found  that  cuprous  chloride  solution  caused  a  contrac- 
tion of  0.5  to  0.6  per  cent  in  Pittsburgh  natural  gas. 
They  have  also  shown  that  a  two-minute  contact  of 
cuprous  chloride  solution  with  pure  ethane  caused  a 
loss  in  volume  of  0.6  per  cent  and  that  in  five  minutes 
the  contraction  was  1.4  per  cent. 

Our  experimental  work  showed  that  those  gases 
which  would  be  expected  to  have  the  largest  proportion 
of  high  molecular  weight  hydrocarbons,  i.  e.,  those 

i  "Oil  and  Gas  Levels."  W.  Va.  Geol.  Survey.  1A  (1904).  552. 
1  "The  Sampling  and  Analysis    of    Mine    and    Natural  Gases,"    Bur. 
of  Mines.  Bull.  42,   46-77. 

(62) 


gases  made  at  low  temperatures  and  fast  rates  of  oil 
feed,  were  also  those  which  showed  the  highest  per- 
centages of  "carbon  monoxide."  It  appeared  certain, 
therefore,  that  the  contractions  found  on  passing  the 
gases  into  the  ammoniacal  cuprous  chloride  solution 
were  in  reality  .largely  due  to  absorption  of  paraffin 
hydrocarbons  such  as  ethane,  propane,  and  butane 
rather  than  to  carbon  monoxide. 

The  use  of  ammoniacal  cuprous  chloride  was  there- 
fore abandoned,  and  the  carbon  monoxide  and  hydrogen 
determined  by  Jaeger's  fractional  combustion  method 
somewhat  as  described  by  H.  C.  Porter  and  G.  B. 
Taylor.1  In  place  of  the  vertical  Nichrome  resistance 
heater  with  the  inverted  U-tube  to  hold  the  copper 
oxide,  a  horizontal  heater  with  a  straight  copper  oxide 
tube  was  used  as  shown  in  the  accompanying  drawing. 


tor  factional  Combustion  o1~CO  tnt  Hz  ovtr  CvO 

The  difference  in  temperature  between  the  bottom 
and  top  of  the  vertical  heater  was  great  enough  so 
that  when  the  oxide  was  at  the  proper  temperature 
in  one  part  of  the  containing  tube,  it  was  either  too 
hot  or  too  cold  in  other  parts  of  the  tube.  With  the 
horizontal  heater  and  the  copper  oxide  tube  running 
concentrically  through  it  no  such  difficulty  was  ex- 
perienced, nor  did  the  water  formed  during  the  com- 
bustion cause  any  trouble. 

The  fractional  combustion  of  gaseous  mixtures  over 
copper  oxide  consumes  a  little  more  time  with  gases 
which  are  low  in  hydrogen  and  high  in  paraffins  than 
does  the  method  in  which  the  cuprous  chloride  pipettes 
and  the  palladium  black  are  used.  However,  as  the 
average  time  for  carefully  made  analyses  is  not  over 
45  mins.,  this  cannot  be  considered  as  a  serious  dis- 
advantage. 

It  was-  found  that  a  temperature  of  275-280°  C. 
burned  the  carbon  monoxide  and  hydrogen  to  carbon 
dioxide  and  water  without  affecting  the  methane 

1  Proc.Am.GasInst.,9  (1914),  255;  J.  Ind'.Eng.  Ghent..  6  (1914).  845-8. 

(63) 


and  other  paraffin  hydrocarbons  present.  After  pass- 
ing the  gases  Over  the  oxide  till  no  further  contraction 
took  place,  they  were  allowed  to  cool  to  room  tempera- 
ture, and  the  volume  read.  The  contraction  at  this 
point  equals  the  per  cent  of  hydrogen  in  the  gas.  The 
carbon  dioxide  was  then  absorbed  in  potassium  hy- 
droxide. This  contraction  is  equal  to  the  per  cent  of 
carbon  monoxide  in  the  gas.  The  importance  of 
allowing  the  gases  to  reach  room  temperature  can 
readily  be  seen.  Otherwise  the  contact  with  the  po- 
tassium hydroxide  will  cause  a  contraction  due  to 
the  lowering  of  the  temperature  of  the  gas. 

The  method  of  burning  the  carbon  monoxide  and 
hydrogen  over  copper  oxide  has  recently  been  dis- 
cussed by  G.  A.  Burrell  and  G.  G.  Oberfell.1  Their 
experiences  with  this  method  were  apparently  similar 
to  ours. 

In  the  case  of  many  of  the  gases  obtained  in  the 
experimental  work,  the  gas  residue  after  the  fractional 
combustion  was  small  enough  so  that  the  whole  of  it 
could  be  mixed  with  oxygen  and  exploded  over  mercury. 
Here  again  the  method  of  burning  over  copper  oxide 
presents  a  distinct  advantage  over  the  methods  first 
mentioned  above,  for  in  the  combustion  with 
palladium  black  it  is  necessary  to  mix  the  gas  with 
oxygen  previous  to  the  fractional  combustion  of  the 
hydrogen.  Thus  a  much  smaller  proportion  of  the 
gas  could  be  put  through  the  partial  combustion  and 
explosion  analysis,  in  consequence  of  which  accuracy 
was  sacrificed.  Accuracy  at  this  point  was  particu- 
larly desired  in  order  to  calculate  the  mean  molecular 
weight  of  the  paraffins. 

AROMATIC     HYDROCARBONS At     the     Outset     of     this 

work  the  desirability  of  determining  the  extent  of  the 
formation  of  hydrocarbons  of  the  benzene  series  was 
evident.  A  careful  survey  of  the  literature,  however, 
showed  that  none  of  the  methods  proposed  had  given 
satisfaction  in  the  hands  of  all  who  had  worked  with 
them.  It  was  not  until  the  work  recorded  here  was 
nearing  completion  that  the  method  proposed  by 
Hulett  and  developed  by  the  Bureau  of  Mines2  came 
to  our  attention.  This  method  was  used  for  the  de- 
termination of  the  aromatics  in  the  gases  from  one 
series  of  runs  at  825°  C. 

1  J.  Ind.  Eng.  Chem.,  8  (1916),  228-231. 

2  G.  A.  Burrell,   F.    M.   Seibert.   and   I.    W.   Robertson,    "Analysis   of 
Natural  Gas  and  Illuminating  Gas  by  Fractional  Distillation  at  Low  Tem- 
peratures and  Pressures,"  Technical  Paper,  104,  26-27. 

(64) 


The  procedure  in  brief  is  to  evacuate  the  apparatus 
with  a  good  pump,  after  which  the  gas  is  admitted 
and  the  temperature  and  barometer  readings  noted. 
The  gas  is  allowed  to  stand  for  some  time  (in  these 
determinations  2  to  3  hrs.),  in  order  that  the  phos- 
phorus pentoxide  may  remove  the  water  vapor 
completely,  and  then  immersed  for  10  to  15  mins. 
in  a  mush  of  carbon  dioxide  snow  in  acetone  contained 
in  a  Dewar  flask.  At  the  end  of  this  time  the  gases 
are  sucked  off  by  means  of  the  pump.  The  bulbs 
are  then  removed  from  the  cold  bath  and  allowed  to 
come  to  room  temperature.  The  temperature  is 
noted  and  the  partial  pressure  of  the  volatilized  aro- 
matics  is  read  on  the  short  arm  manometer.  From 
this  data  the  volumetric  percentage  of  these  com- 
ponents in  the  gas  can  be  calculated.  A  rotary  oil 
pump  which  gave  a  vacuum  of  less  than  i  mm.  of 
mercury,  and  that  in  less  than  a  minute,  was  used  in 
these  experiments. 

MEAN  MOLECULAR  WEIGHT  OF  THE  OLEFINS 

When  the  analysis  and  the  specific  gravity  of  a  gas 
are  known  the  mean  molecular  weight  of  the  heavy 
hydrocarbons  of  the  gas  can  be  calculated.  When, 
in  addition  to  the  percentages  of  carbon  dioxide, 
heavy  hydrocarbons,  oxygen,  carbon  monoxide,  hy- 
drogen, methane,  ethane,  and  nitrogen,  the  percentage 
of  aromatics  is  known,  the  mean  molecular  weight  of 
the  olefins  and  acetylenes  can  be  calculated. 

In  determining  the  specific  gravity  the  temperature 
of  the  gas  and  the  barometer  reading  should  be  taken,  and 
the  gas  should  be  thoroughly  shaken  with  water  in  order 
to  saturate  it  with  water  vapor  at  the  temperature  of 
the  room  before  introducing  it  into  the  specific  gravity 
apparatus.  Time  should  be  allowed  for  the  subsidence 
of  any  mist  formed  during  the  agitation  with  water. 

The  method  used  for  the  determination  of  the 
specific  gravity  was  the  so-called  effusion  method  and 
the  apparatus  was  similar  to  that  described  by  Pan- 
nertz.1  The  orifice  was  made  by  pricking  a  piece 
of  thin  platinum  foil  with  a  needle,  and  then  beating 
the  foil  with  a  small  leather  mallet  till  the  tiny  hole 
was  visible  only  when  held  up  to  a  strong  light.  This 
foil  was  mounted  on  the  end  of  a  short  brass  tube 
fitting  with  a  carefully  turned  brass  screw  cap  luted  in 
with  litharge  and  glycerol  cement. 

Certain  errors  are  inherent  in  the  experimental 
methods  used.  In  the  first  place  it  is  well  known  that 

»  J.  fUr  Gasbel,  48  (1905),  901. 

(65) 


fuming  sulfuric  acid  absorbs  higher  paraffins  during 
the  determination  of  the  heavy  hydrocarbons.1  It 
was  thought  that  the  use  of  bromine  water  might 
obviate  this  difficulty,  but  analyses  on  621°  C.  gases 
made  by  both  methods  checked  to  within  o.i  per  cent 
showing  that  the  two  reagents  were  having  similar 
effects.  F.  C.  Phillips'2  says  that  bromine  water  ab- 
sorbs the  higher  paraffins. 

Disagreement  between  analyses  made  by  the  use  of 
bromine  water  and  by  fuming  sulfuric  acid  may  be 
occasioned  by  the  fact  that  bromine  water  does  not 
brominate  benzene.  In  the  analyses  made  in  these 
experiments  there  is  little  doubt  but  that  the  benzene 
would  have  been  completely  scrubbed  down  on  ac- 
count of  the  time  and  shaking  necessary  to  obtain 
complete  reaction  between  the  olefins  and  the  bromine 
solution.  Also  the  proportion  of  benzene  present  in 
a  621  °  C.  gas  made  at  atmospheric  pressure  is  not  large. 

The  absorption  of  higher  paraffins  by  the  fuming 
sulfuric  acid  can  be  avoided  in  large  part  by  the  use  of 
small  portions  of  the  reagent  in  an  apparatus  of  the 
type  described  by  G.  B.  Taylor.3  It  was  thought, 
however,  that  the  time  required  for  analyses  made  in 
this  way  would  be  too  great. 

Another  error  inherent  in  the  method  of  determining 
the  mean  molecular  weight  of  the  olefins  lies  in  the  fact 
that  the  method  for  aromatics  does  not  differentiate 
between  benzene,  toluene,  or  xylene.  An  average 
molecular  weight  must  be  assumed  here  which  evidently 
is  not  absolutely  correct.  In  the  calculations  all 
aromatics  have  been  regarded  as  if  they  were  benzene, 
since  it  was  believed  that  this  hydrocarbon  comprised 
the  greatest  portion  of  the  aromatics  present  in  the- gas. 

A  further  error  lies  in  the  fact  that  the  paraffins 
were  all  assumed  to  be  methane  and  ethane.  Higher 
homologs  of  this  series  are  without  doubt  present  as  has 
been  shown  by  Burrell,  Seibert,  and  Robertson  in  their 
analyses  of  carbureted  water  gas  and  coal  gas  by  the 
method  of  fractional  distillation  at  low  temperatures.4 

A  certain  proportion  of  naphthenes  or  polymethylenes 
are  also  no  doubt  present  among  the  products  of  the 
pyrogenic  decomposition  of  the  hydrocarbons  of 

»  R.  P.  Anderson  and  J.  C.  Engelder,  J.  Ind.  Eng.  Chem.,  6  (1914),  989- 
92;  R.  A.  Worstall,  J.  A.  C.  S.t  21  (1899),  245;  Orndorff  and  Young,  Am. 
Chem.  J..  15  (1893),  249;  Burrell  and  Seibert,  "Sampling  and  Analysis  of 
Mine  and  Natural  Gas,"  Bur.  of  Mines,  Bull  42  (1913),  45-47. 

*  "Oil  and  Gas  Levels,"  W.  Va.  Geol.  Survey,  1A  (1904),  522. 

a  J.  Ind.  Eng.  Chem.,  6  (1914).  845. 

4  Bureau  of  Mines,  Tech.  Paper,  104  (1915);  J.  Ind.  Eng.  Chem.,  7 
(1915),  17-21. 

(66) 


kerosene.  To  what  extent  these  are  affected  by  the 
fuming  sulfuric  acid,  and  to  what  extent  they  are  carried 
through  the  analysis  and  credited  to  the  paraffins 
cannot  be  stated.  Data  on  the  exact  behavior  of  the 
cyclobutanes,  cyclopentanes,  and  cyclohexanes  when 
treated  with  fuming  sulfuric  acid  have  not  been  found, 
if,  in  fact,  such  information  is  at  all  available. 

In  addition  to  the  errors  already  mentioned  is  the  ex- 
perimental error  in  the  determination  of  the  specific 
gravity  by  the  effusion  method.  Check  determinations 
were  always  made  on  the  time  of  flow,  and  it  was  found 
possible  to  get  agreements  to  within  less  than  o.  5  per  cent. 

The  following  analyses  are  cited  to  compare  the 
results  obtained  by  the  usual  procedure  with  Hempel 
burette  and  pipettes  with  those  obtained  by  the  use 
of  the  various  modifications  discussed  above.  These 
will  be  designated' for  the  sake  of  brevity  as  the  "Stand- 
ard" method  and  the  "CuO"  method,  respectively. 

GAS  No.  24  GAS  No.  24  GAS  No.  25 

METHOD:  Standard       CuO       Standard  CuO  Standard  CuO 

Carbon  dioxide... 0.3        0.0       0.1        0.1  0.1  0.0  0.0 

Heavy  hydrocarbons. ..      48.1      48.2     47.9  49.8  49.3  50.8  507 

Oxygen 0.5       0.5       0.5       0.5  0.5  0.4  0.4 

Carbon  monoxide 1.2       0.2        0.2       0.9  0.1  1.1  01 

Hydrogen 11.9      11.9     12.1       9.3  9.2  10.4  10.3 

Paraffins 37.3     37.6     37.7  38.1  38.4  37.0  37.2 

Total 99.3     98.4     98.5     98.7        97.6      99.7         98.7 

THE    GAS    RATE 

The  gas  rates  for  three  temperatures  are  plotted 
against  the  oil  rates  in  Fig.  8.  At  621°  C.  the  gas  rate 


as 

per 

VARIATION  OP  GAS  RATE  WITH  VARIOUS  OIL  RATBS  AT  THREE 
TEMPERATURES 

increases  with  the  oil  rate  up  to  an  oil  rate  of  20  cc.  per 
minute,  but  the  introduction  of  more  oil  per  minute 
causes  no  further  increase  in  the  gas  rate.  Apparently 

(67) 


with  a  heated  tube  of  the  dimensions  used  here  only  a 
certain  quantity  of  oil  can  be  affected  in  a  given  time 
by  heat  at  a  temperature  of  621°  C.  A  similar  limita- 
tion would  be  expected  in  a  commercial  machine 
operating  at  this  temperature.  At  723°  C.  the  gas 
rate  is  greater  with  greater  oil  rate  at  all  oil  rates 
studied.  Judging  from  the  shape  of  the  curve  and 
from  the  analogy  of  the  621°  C.  curve  it  is  apparent 
that  an  increase  in  oil  rate  above  45  to  50  cc.  per  minute 
would  produce  no  increase  in  the  gas  rate.  At  825°  C. 
the  gas  rate  increases  with  increase  in  oil  rate  as  can  be 
seen,  and  at  the  oil  rates  studied  there  is  no  apparent 
tendency  for  a  rate  to  be  reached  beyond  which  there 
is  no  further  increase.  Obviously,  however,  such  a 
point  would  be  reached. 

In  comparing  the  gas  rate  curves  it  is  interesting  to 
note  that  at  low  oil  rates  the  change  in  temperature 
from  62 1  to  723°  C.  has  a  much  greater  effect  than 
the  change  from  723  to  825°  C.  At  low  oil  rates 
a  temperature  of  723°  C.  is  sufficient  to  gasify  per- 
manently the  greatest  portion  of  the  oil.  The  slightly 
greater  production  of  gas  at  825°  C.  is  largely  due  to 
the  decomposition  of  methane  into  carbon  and  hydrogen. 

As  the  oil  rate  increases,  a  temperature  of  723°  C. 
becomes  less  and  less  effective  for  the  purpose  of  per- 
manently gasifying  the  oil;  825°  C.  is  much  more 
effective,  as  can  be  seen  from  the  increasing  divergence 
between  the  curves. 

THE  DECOMPOSITION  OF  PARAFFIN  HYDROCARBONS 

Figs.  9  to  14  indicate  the  proportions  of  the  various 
components  obtained  when  the  oil  was  decomposed 
alone.  Fig.  9  shows  that  at  621°  C.  the  gases  are 
composed  of  about  10  per  cent  hydrogen  at  all  oil 
rates  above  5  cc.  per  minute.  The  reactions  which 
contribute  to  the  formation  of  this  hydrogen,  named 
in  order  of  their  probable  importance,  are: 

(/)      C2H6  ^±  C2H4  +  H2 

00     C2H4  :^±  C2H2  +  H2 

(3)  CH4   — ^  C        +  2H2 

(4)  C2H2  — ->  2C      +  H2 

The  conditions  are  those  which  are  known  to  be 
favorable  to  the  condensation  of  acetylene.  The 
methods  for  the  determination  of  acetylene  are  so 
unsatisfactory  that  no  effort  was  made  to  determine 
the  proportion  of  acetylene  in  the  gases  formed. 
Other  investigators  have  found  the  amount  small  in 
similar  experiments. 

(68) 


IV 

60 
SO 
40 

:30 

& 

g20 

*J 
^ 

fc/o 

^ 

0 

r/G 

.  9 

\ 

s 

^ 

—  82^ 

_\ 

•*-«  . 
-~i 

9 
~ 

3 

>=^ 

723' 
~65? 

M= 

&  

Oil 

10         /5"        20        25       30        35       40       45        J 

Rate  -  cc.  p<rr    minute          —  - 

10 


\v 

t.« 

r/c. 

10 

1 

-Q  50 

\ 

k  ^^ 

1. 

^L 

*JO 

XJ 

^^n 

> 

X. 

•^^ 

>7?Vr 

'*~          - 

.       ~^^ 

-*  — 

*=Z 

• 

- 

<-$ 

'5*C 

| 

^  /0 
^? 
0 

J         /O         /5       20       25       JO        J5       4(5       45"       J- 

0/7    /?flf<r  -  c.c.  per  minute        —  - 

75        20        25        30        35 

Oif    Rate  -  cc.  per   minute 


(69) 


The  rapid  increase  in  the  proportion  of  hydrogen 
with  decreasing  oil  rates  below  5  cc.  per  minute  is 
thought  to  be  due  to  a  marked  increase  in  the  extent 
to  which  reactions  (j)  and  (4)  take  place.  At  723°  C. 
only  a  slightly  larger  proportion  of  hydrogen  is  formed 
than  at  621°  C.,  indicating  that  reactions  (j)  and  (4) 
do  not  become  rapid  up  to  this  temperature.  A  very 
marked  increase  in  the  hydrogen  production  takes 
place  when  the  temperature  is  elevated  to  825°  C., 
chiefly  due  to  an  increase  in  reactions  (3)  and  (4),  as  is 
evidenced  by  the  very  large  amount  of  free  carbon 
which  was  liberated  and  which  tended  to  stop  the 
furnace  tube.  No  trouble  was  occasioned  by  this 
carbon  deposition  at  621°  C.  or  723°  C. 

Fig.  ii  shows  the  proportion  of  illuminants,  or  com- 
ponents removed  by  20  per  cent  fuming  sulfuric  acid, 
in  the  oil  gases  made  at  the  three  temperatures.  The 
percentage  of  illuminants  is  highest  in  the  gases  made 
at  62i°C.  at  all  oil  rates,  and 'remains  practically 
constant  at  52  per  cent  at  all  oil  rates  above  10  cc.  per 
minute.  The  proportion  of  illuminants  formed  at 
723°  C.  is  higher  than  at  825°  C.  except  possibly  at 
high  Oil  rates.  It  is  thought,  however,  that  the  pro- 
portion of  illuminants  at  high  oil  rates  would  not  be 
greatly  different  at  any  of  these  temperatures. 

The  fact  that  the  proportion  of  illuminants  is  lower, 
the  higher  the  temperature  at  moderate  to  low  oil 
rates  is  due  to  the  secondary  reactions  of  these  hydro- 
carbons. Ethylene  is  decomposed  into  carbon  and 
methane  to  some  extent.  Condensation  to  naphthenes 
takes  place.  At  these  low  oil  rates  the  proportion  of 
hydrogen  present  is  considerable,  and  the  higher  the 
temperature  the  higher  this  percentage.  Hence  it 
would  be  expected  that  hydrogenation  reactions  such 
as  C2H4  +  H2  ^±  C2H6  and  C2H4  +  2H2  ^±  2CH* 
would  take  place. 

The  relation  between  the  proportions  of  saturated 
hydrocarbons  formed  at  different  temperatures  is 
shown  in  Fig.  10.  It  can  be  seen  that  the  proportion 
of  saturateds  in  the  gas  is  higher  at  723°  C.  than  at 
621°  C.  at  all  oil  rates.  This  no  doubt  is  due  to  the 
faster  speeds  of  such  reactions  as  C2H4  — >•  C  +  CHi 
and  C2H6  +  H2  ^±1  2CH4. 

It  might  reasonably  be  expected  that  the  percentage 
of  saturateds  in  the  gases  would  be  greater  at  825°'  C. 
than  at  723°  C.,  but  it  can  be  seen  from  Fig.  10  that 
this  is  not  the  case.  At  low  oil  rates  the  proportion 
of  saturateds  is  lower  at  825°  C.  than  at  723°  C. 

(70) 


JO 

60 
50 
An 

62 

/°C 

r/G. 

12 

///j. 

V 
7 

X 
v^ 

ir 

/0  componem 

•—  N>  C4  J 
O  O  O  O  < 

/ 

r 

\ 

/>i 

• 

Oil 

r          10          15        20         25        30         35        4O        4-5         J< 

y9afe  -  cc.  per    minute          —  - 

/  u 

60 
50 
40 
30 
20 
10 
O 

723 

'C 

ri&. 

/  J 

\ 

V 

nit. 

<r 

Sat. 

f 

/" 

1 

^ 

~-°—  . 

> 

Oil 

/O        IS        20        25"        J( 

Rate  -  cc.  per    mi 

rwte  

/O         /5        20        25        JO        JJ        ^0        45        SO 

Oil    Rate  -  cc.  per    minute 


(71) 


This  is  chiefly  due  to  the  fact  that  the  reaction 
CH4  — >  C  -f  2H2  has  an  appreciable  velocity  at  this 
temperature.  As  the  oil  rate  increases  it  would  be 
reasonable  to  expect  that  the  effect  of  this  reaction 
would  be  less  and  less.  However,  the  divergence  be- 
tween the  825°  C.  curve,  and  the  723°  C.  curve  be- 
comes greater  the  faster  the  oil  rate.  This  state  of 
affairs  is  apparently  due  to  the  superimposed  effect  of 
another  reaction.  When  the  high  paraffin  hydro- 
carbons first  break  down  under  these  conditions  the 
chief  products  are  low  molecular  weight  paraffin 
hydrocarbons  and  high  molecular  weight  olefins.  At 
621°  C.  and  723°  C.  a  considerable  proportion  of  the 
high  molecular  weight  olefins  formed  pass  on  through 
the  tube  into  the  tar.  The  tars  were  larger  in  amount 
the  lower  the  temperature,  and  when  the  tar  curves 
are  studied  it  will  be  seen  that  there  is  not  a  marked 
difference  between  the  tar  formation  at  621°  C.  and 
723°  C.  but  that  a  considerable  difference  is  found  at 
825°  C.  These  low  temperature  tars  were  treated 
with  concentrated  sulfuric  acid  in  the  cold,  and  it  was 
found  that  20—25  Per  cent  by  volume  was  removable  in 
this  fashion,  the  greater  portion  of  which  was  doubt- 
less olefins  of  high  molecular  weight.  At  825°  C.  the 
effect  of  the  heat  is  sufficient  to  break  down  these 
higher  olefins  almost  completely.  In  the  process 
ethylene  and  propylene  are  formed  in  large  quantity 
with  the  result  that  the  percentage  of  saturated 
hydrocarbons  drops.  The  proportion  of  illuminants 
and  saturated  hydrocarbons  present  in  the  gases  at 
825°  C.  is  greatly  lowered  on  account  of  the  high 
percentage  of  hydrogen  present  in  these  gases. 

Figs.  12,  13  and  14  show  the  relations  between  the 
component  illuminants,  saturateds,  and  hydrogen  at 
the  temperatures  621°  C.,  723°  C.  and  825°  C., 
respectively.  Of  all  the  proportions  of  these  com- 
ponents those  at  the  high  oil  rates  at  621°  C.  most 
nearly  represent  the  products  of  the  primary  decom- 
position of  the  oil.  The  hydrogen  is  largely  the  re- 
sult of  secondary  reactions.  If  the  illuminants  and 
saturateds  are  calculated  to  a  100  per  cent  basis  the 
proportion  is  58  per  cent  illuminants  and  42  per  cent 
saturateds.  Such  a  ratio  as  this  would  be  expected  in 
the  reaction  if  the  primary  decomposition  of  the 
paraffin  was: 

CwH2M  +  2  — >•  CM_iH2«-2  +  CH4 
Paraffin  Olefin 

(72) 


and,  if  then,  the  high  molecular  weight  olefins  in  part 
broke  down  to  lower  olefins. 

The  mechanism  of  the  reactions  at  work  can  be 
judged  somewhat  from  a  consideration  of  the  relations 
between  the  curves  for  the  percentages  of  illuminants, 
saturateds,  and  hydrogen.  Thus,  in  Fig.  12,  if  it  is 
assumed  that  the  illuminants  are  chiefly  ethylene  and 
the  saturateds  largely  methane  it  can  be  seen  that  the 
normal  formation  of  ethylene  is  52,  that  of  methane 
39,  and  that  of  hydrogen  10  per  cent. 

Consider  the  proportions  in  the  gas  at  an  oil  rate 
of  2.5  cc.  per  minute.  They  are  ethylene  34,  methane 
50,  and  hydrogen  16  per  cent.  The  decrease  in 
ethylene  has  been  18  per  cent  on  the  basis  of  the  total 
gas.  If  this  had  been  due  to  the  reaction  C2H4  —  > 
C  +  CH4  the  methane  should  have  increased  18  per 
cent  on  the  basis  of  the  total  gas.  In  fact  it  increases 
only  ii  per  cent. 

The  hydrogen  increases  6per  cent  on  thetotal  gas  basis. 
If  this  were  due  to  the  reaction  CH4  —  >  C  4-  2H2 
a  3  per  cent  decrease  in  the  methane  should  have  taken 
place.  But  as  has  been  seen,  other  reactions  also  give 
rise  to  hydrogen.  Assuming,  however,  that  the  above 
reaction  was  the  sole  change  of  this  sort,  only  14  per 
cent  out  of  the  18  per  cent  increase  in  methane  which 
should  have  been  found,  had  the  ethylene  reacted 
entirely  with  formation  of  carbon  and  methane,  would 
be  accounted  for.  Hence  the  ethylene  must  be  re- 
moved in  other  ways,  for  example  by  the  condensation 
to  naphthenes. 

It  is  not  probable  that  the  6  per  cent  increase  in  the 
hydrogen  is  entirely  due  to  the  decomposition  of 
methane.  Dehydrogenation  of  naphthenes,  dissocia- 
tion of  ethylene  and  ethane,  etc.,  may  give  rise  to 
hydrogen.  Then,  too,  not  all  the  methane  formed 
comes  from  the  decomposition  of  ethylene.  Decom- 
position of  higher  olefins  in  such  a  manner  as 


CH4  +  CH2=CH—  CH=CH2 

and  hydrogenation  of  olefins,  C2H4  +  2H2  <  >  2CH4, 
may  contribute. 

A  similar  argument  may  be  worked  out  for  the  rela- 
tion between  the  illuminants,  saturateds,  and  hydrogen 
at  723°  C.  and  825°  C. 

The  marked  decrease  in  illuminants  with  decreasing 
oil  rates  at  825°  C.  is  notable.  No  corresponding 
increase  in  saturateds  takes  place.  It  is  apparent 

(73) 


(U 

«o   60 
10  50 

S. 

r/G 

/5 

* 

Illj. 

/^ 

6    ° 

^   30 

^ 

6 

T    f 

|  20 
|   10 

Oil 

yd  5 
705  ^ 

/*    : 

± 

0 

6 

62/'< 

:    //• 

;« 

0 

I10 

Oil 

10        IS        20       25       JO        J5       40       45       50 

Atafe  -  cc.  per   minute  

\ 

r/c 

.  /6 

^ 

///^. 

ff^^ 

0 

'  •  4f\ 

W 

*5*^— 

s 

/ 

%  Component 

—  r  N*  < 
O  0  0  C 

Oil 

Oil  ( 

;as  y 

^: 



0 

6 

7; 

:rc 

/"; 

:26 

ers 

Oil 

10                       /x 

Rate  -  c 

r        20        25        JO         J5       4O        45        JO 

•c.  per    minute  

t  /u 

to 

'^  60 
^J 

CO 
^  50 
£ 

i*° 

^- 
30 

•v» 

|20 

h 

Vj 
^    0 

x\° 
\\ 

no 

,/7 

V 

cTS* 

juL 

—4 

<s 

60*" 

2 

^| 

6 

6<* 

Sot 

--J 

y/ 
/° 

7 

0/7  G 
Oil  G 

as 

fl-S   V- 

HZ   - 

o 
d 

723- 

C     2 

H2:l 

yds 

S         10        15        20       25        30        3f       40       *5"        / 

Oil    Rate   -   cc.  per  minute   -  —  *• 

(74) 


from  the  high  percentage  of  hydrogen  that   methane 
is  decomposing  extensively  into  carbon  and  hydrogen. 

PROPORTION    OF    ILLUMINANTS    AND    SATURATED    HYDRO- 
CARBONS 

In  order  that  the  effect  of  hydrogen  on  the  com- 
position of  the  gases  as  regards  illuminants  and  satu- 
rated hydrocarbons  may  be  seen,  Figs.  15,  16,  17,  18 
and  19  are  shown.  These  curves  were  drawn  by 
calculating  the  illuminants  and  saturated  hydro- 
carbons to  a  basis  of  100  per  cent.  In  this  manner  the 
proportions  of  the  two  classes  of  compounds  can  be 
seen. 

It  might  be  expected  that  hydrogenation  reactions 
would  play  an  important  part  and  that  the  proportion 
of  saturated  hydrocarbons  would  be  higher  in  the  oil- 
gas-hydrogen  runs  than  in  the  straight  oil-gas  runs. 
It  will  be  shown  later  in  this  paper  that  hydrogenation 
does  take  place  to  a  considerable  extent. 

It  should  be  noticed  that  at  low  temperatures  the 
presence  of  the  hydrogen  has  no  influence  on  the 
relative  amounts  of  illuminants  and  saturated  hydro- 
carbons at  high  oil  rates;  i.  e.,  its  presence  has  little 
effect  on  the  mechanism  of  the  primary  decomposition 
and  the  early  stages  of  the  secondary  decomposition. 
But  at  low  oil  rates  where  the  gases  are  exposed  to  the 
effect  of  heat  for  a  longer  time,  and  where  extensive 
secondary  and  tertiary  changes  take  place  the  hydrogen 
has  a  considerable  influence  at  temperatures  of  723°  C. 
and  825°  C.  At  621°  C.  the  influence  of  the  hydrogen 
is  not  marked. 

It  will  be  remembered  that  the  first  reaction  under- 
gone by  a  paraffin  hydrocarbon  when  it  is  thermally 
decomposed  is  that  which  gives  rise  to  a  high  molecular 
weight  olefin  and  a  low  molecular  weight  paraffin. 
It  is  probable  that  the  higher  the  molecular  weight  of 
an  olefin  the  more  readily  it  is  hydrogenated. 

If  the  high  molecular  weight  olefins  are  hydro- 
genated paraffins  would  be  formed.  These  would 
again  decompose  into  long  chain  olefins  and  low 
molecular  weight  paraffins.  This  sequence  of  re- 
actions may  be  represented  as  follows: 

CMH2«  +  2  — >  CM-iH2«-2  +  CH4 
Paraffin  Olefin 

CM  —  1  H2n  —  2    +    H2  >    Cn  —  1  H2n 

Olefin  Paraffin 

Cn  —  1  H2n  *"    CM  —  2H2n  —  4    +    CH4 

Paraffin  Olefin 

(75) 


The  net  result  of  such  a  sequence  of  reactions  would 
be  an  increase  in  the  proportion  of  paraffins  in  the 
gas.  But  as  can  be  seen  in  the  figures,  the  proportion 
of  paraffins  is  less  in  the  cases  of  the  hydrogen-oil 
gases.  However,  at  high  oil 'rates  where  secondary 
reactions  are  not  so  important,  and  in  the  series  of 
runs  at  825°  C.  where  the  concentration  ratio  was 


IO        15       20        25        JO        35       40       45        5( 

Oil   Rate  -  cc.  per   minute 


40       45 


^0 


0  5         10        15       20        25       30        35 

Oil    Rate    -  cc.  per     minute    -   — - 

2H2  :  i  gas  (Figs.  17  and  19),  the  proportion  of 
saturated  hydrocarbons  is  greater  in  the  hydrogen-oil- 
gas  runs.  It  is  probable,  therefore,  that  the  above 
reactions  take  place  in  all  cases  but  that  the  effect  of 
the  hydrogen  at  low  oil  rates  on  the  extensive  secondary 

(76) 


changes  is  so  great  that  the  result  of  the  hydrogenation 
is  masked. 

Apparently  the  low  molecular  weight  olefins  are  not 
hydrogenated  to  a  large  extent,  for  were  this  'the  case 
the  proportion  of  saturated  hydrocarbons  present 
would  be  greatly  increased.  This  is  not  the  case. 

The  increase  in  the  proportion  of  olefins  in  the 
hydrogen-oil-gas  runs  at  low  rates  of  oil  feed  may  be 
accounted  for  in  two  ways: 

(i) — The  effect  of  the  hydrogen  may  be  to  increase 
those  reactions  which  give  rise  to  olefins. 

(2) — The  effect  of  the  hydrogen  may  be  to  retard 
those  reactions  which  tend  to  remove  or  destroy  the 
olefins. 

The  largest  proportion  of  the  ethylene  and  propylene 
present  comes  from  the  direct  splitting  up  of  high 
molecular  weight  olefins.  If  an  olefin  of  fairly  high 
molecular  weight  may  be  used  to  illustrate,  this  re- 
action may  be  represented: 
CH3CH2CH2CH=CH2 — ^CH3CH=CH2  +  CH2=CH2 

It  will  be  noticed  that  the  result  is  an  increase  in 
volume.  The  equilibrium  point  of  the  reaction  would 
therefore  be  shifted  by  a  diminution  of  pressure  in 
such  direction  as  to  favor  the  production  of  ethylene 
and  propylene.  The  introduction  of  hydrogen  has  the 
same  effect  as  a  reduction  in  pressure,  and  would 
therefore  have  a  similar  effect  on  the  equilibrium. 

Chief  among  the  reactions  which  remove  olefins 
such  as  ethylene  and  propylene  are  condensation 
and  decomposition.  These  reactions  may  be  rep- 
resented as  3C2H4  — >  C6Hi2  and  C2H4  — >•  C  +  CH4, 

The  presence  of  the  hydrogen  would  displace  the 
equilibrium  point  of  the  first  of  these  reactions  in 
favor  of  the  ethylene.  The  latter  reaction,  insofar 
as  the  influence  of  volume  relationships  on  the  equilib- 
rium point  is  concerned,  would  not  be  affected. 

Whether  the  displacement  of  the  equilibrium  points 
in  any  of  these  reactions  is  sufficient  to  be  worthy  of 
mention  can  not  be  said.  In  no  case  is  the  equilibrium 
condition  attained,  but  the  speeds  of  the  various  re- 
actions would  depend  on  the  difference  between  the 
actual  condition  of  the  system  and  the  equilibrium 
condition;  hence  any  displacement  of  the  equilibrium 
point  would  be  important. 

The  increase  in  the  proportion  of  olefins  may  be 
looked  upon  from  another  angle.  When  hydrogen  is 
introduced  along  with  the  gas  the  time  of  contact  of 
the  gas  with  the  heated  tube  is  diminished,  due  to  the 

(77) 


increase  in  the  total  volume  passing  in  unit  time.  If 
it  is  the  case  that  the  reactions  which  give  rise  to  the 
olefins  ethylene  and  propylene  are  fairly  rapid,  while 
those  which  destroy  them  are  slower,  the  summational 
effect  of  an  increased  gas  rate  would  be  an  increased 
proportion-  of  olefins.  That  the  speed  of  the  re- 
actions which  produce  olefins  is  fairly  great  can  be 
seen  by  reference  to  Fig.  22,'  which  shows  the  mean 
molecular  weight  of  the  olefins  formed  at  825°  C. 
The  mean  molecular  weight  lies  between  30  and  34. 
The  molecular  weight  of  ethylene  is  28,  while  that  of 
propylene  is  42.  The  proportion  of  olefins  higher 
than  propylene  cannot  be  great,  therefore,  and  it 
would  seem  that  they  break  down  largely  to  ethylene 
and  propylene.  That  the  reactions  which  cause  a 
removal  or  destruction  of  ethylene  are  only  moderate 
in  speed  has  been  seen  under  the  discussion  of  the 
reactions  of  ethylene  in  the  first  part  of  this  paper. 

This  latter  explanation  appears  more  probable  than 
the  one  concerning  the  displacement  of  the  equilib- 
rium points  of  reactions;  however,  both  of  these 
effects  may  be  concerned  in  the  production  of  the  re- 
sults observed. 

It  will  be  noticed  that  the  two  different  hydrogen 
concentrations  produce  similar  results  at  723°  C.  but 
that  at  825°  C.  the  proportion  of  olefins  is  much 
higher  when  the  concentration  ratio  is  2 HI  :  i  Gas. 
The  rather  large  difference  in  this  last  case  indicates, 
that  the  chief  effect  of  the  hydrogen  is  due  to  its 
cutting  down  the  time  of  heating,  for  at  825°  C.  the 
decomposition  of  the  higher  olefins  to  ethylene  is 
doubtless  very  rapid,  and  takes  place  extensively  in 
spite  of  the  reduced  time  of  heating  in  the  hydrogen- 
oil  gas  runs. 

THE    ABSORPTION    OF    HYDROGEN 

Calculations  from  the  analytical  data  show  that  a. 
considerable  absorption  of  hydrogen  takes  place  when 
the  oil  is  cracked  in  an  atmosphere  of  this  gas.  Haber 
was  of  the  opinion  that  the  oil  produced  no  hydrogen 
by  its  own  decomposition  when  it  was  cracked  in  an 
atmosphere  of  hydrogen.  On  the  other  hand,  it  might 
be  assumed  that  there  would  be  as  much  hydrogen 
produced  under  these  conditions  as  when  the  oil  was 
cracked  alone.  These  two  assumptions  offer  two  bases 
on  which  the  absorption  gf  hydrogen  may  be  calcu- 
lated. 

(i) — If  no  hydrogen  is  produced  by  the  cracking 
of  the  oil,  the  hydrogen  absorption  per  cc.  of  oil  would 

(78) 


be  equal  to  the  difference  between  the  hydrogen  added 
and  that  present  in  the  final  gas  divided  by  the  total 
number  of  cc.  of  oil. 

(2) — If  the  oil  produces  as  much  hydrogen  as  when 
cracked  alone,  the  difference  between  the  hydrogen 
added  plus  that  normally  produced  from  the  oil  at  the 
particular  oil  rate  and  the  hydrogen  in  the  final  gas 
represents  the  absorption.  This  divided  by  the  total 
number  of  cc.  of  oil  gives  the  absorption  in  cc.  per 
cc.  of  oil. 

Fig.  21  shows  the  absorption  per  cc.  of  oil  calcu- 
lated on  basis  (i)  for  the  several  temperatures  and 
concentrations.  Fig.  22  shows  these  absorptions  calcu- 
lated on  basis  (2). 

It  will  be  seen  that  the  curves  of  Fig.  22  are  much 
smoother  and  more  regular  than  those  of  Fig.  21,  not 
because  they  are  drawn  more  smoothly,  but  because 
the  points  fall  on  smoother  curves.  The  general  form 
of  the  curves,  too,  in  Fig.  22  is  that  which  would  be 
expected  from  a  consideration  of  the  curves  for  the 
hydrocarbon,  components  formed  per  cc.  of  oil.  The 
curves  of  Fig.  21  show  no  general  similarity  to  each 
other,  while  those  of  Fig.  22  show  similar  general 
characteristics.  The  curves  representing  the  forma- 
tion of  all  the  other  components  of  the  gases  show 
regular  variations,  and  it  would  be  expected  that  this 
regularity  would  extend  to  the  curves  for  hydrogen 
absorption. 

In  general,  therefore,  it  seems  that  the  basis  on 
which  the  curves  of  Fig.  22  are  calculated  is  more 
nearly  correct  than  the  basis  which  assumes  that  no 
hydrogen  is  produced  from  the  oil  when  it  is  decom- 
posed in  hydrogen.  This  view  is  strengthened  by 
the  fact  that  in  the  case  of  the  825°  C.  gases  with 
hydrogen  concentrates  iH2  :  2  Gas,  the  absorption 
curve  in  Fig.  21  falls  below  the  o.o  line,  i.  e.,  hydrogen 
must  have  been  formed  from  the  oil  since  there  was 
more  hydrogen  in  the  final  gas  than  was  added  through 
the  meter. 

It  is  probable  that  the  true  value  for  the  hydrogen 
absorptions  for  any  set  of  conditions  falls  between  the 
two  values  as  calculated  from  the  two  limiting  as- 
sumptions. It  is  thought  that  the  true  values  are 
slightly  less  than  the  values  of  the  absorptions  as  they 
would  be  read  from  the  curves  in  Fig.  22. 

The  curves  of  Fig.  22  show  the  interesting  fact  that 
at  any  particular  temperature  the  hydrogen  absorption 
per  cc.  of  oil  decreases  with  increasing  oil  rate.  The 

(79) 


200 


i 


I  ' 


^ 


8?  5V 


8; 


r/s. 


1  6as 


"ZTC 


0         3         10         IS        ZQ        25        JO        JJ        40       45        JO 

Ci          Oil     Rate    -  cc.    per     minute    - 

«<  -ten, . 

in 

I 


§ 


8 


g 


ISO 


-  cc.    per    minute 


t: 

fcr 

§30 
0 

825 

t 

IHt: 

2G( 

15 

no. 

25 

^^f*^ 

0— 



-^    I0 

5.0 

v*> 

out 

Oil  6 

as 

flS     + 

//,  - 



J           /O           /J-         2(?         2S         30         35         40          45         S 

Oil   Rate  -  cc.   per    minute.  - 

BZ5' 

'", 

1*  i 

^6a 

PIG. 

£4 

*~~    30 

Q   20 

Oil  (. 
Oil  ( 

*l  , 

*/y,- 

-- 

D 

-o- 

^    1.0 

o—  "^^ 

0            ->         /O        /i        20       2i        JO       J5        40      45       J 

Oil    Rate   -  cc.  per    minute    
(80) 

great  importance  of  the  time  factor  is  well  brought 
out  here.  At  constant  oil  rate,  and  approximately 
the  same  hydrogen  concentration  the  absorption  per 
,  cc.  of  oil  is  greater  the  higher  the  temperature.  There 
would,  however,  be  an  upper  limit  to  this  on  account 
of  the  excessive  decomposition  of  all  hydrocarbons  at 
elevated  temperatures. 

The  effect  of  increasing  the  concentration  of  hy- 
drogen is  clearly  shown  in  Fig.  22,  for  the  curve  for  the 
2 Hz  :  i  Gas  runs  in  above  the  curve  for  the  iHz  :  2 
Gas  runs  at  both  723°  C.  and  825°  C.  The  spee.d  of 
hydrogenation  reactions  is  greater  the  higher  the 
concentration  of  hydrogen. 

It  is  interesting  to  note  that  the  curve  for  the 
i H2  :  2  Gas  runs  at  825°  C.  falls  below  the  curve  for 
the  2 Hz  :  i  Gas  runs  at  723°  C.  This  shows  that  the 
increasing  temperature  is  tending  to  cause  dehydro- 
genation  reactions  or  hydrocarbon  dissociations  to  a 
marked  degree  at  825°  C.  The  effect  of  hydrogen 
in  greater  concentration  in  reversing  these  dissocia- 
tions is  clearly  brought  out  when  the  position  of  the 
2 H2  :  i  Gas  curve  for  825°  C.  is  considered  in  its 
relation  to  the  iH2  :  2  Gas  curve  at  this  same  tempera- 
ture. 

MEAN    MOLECULAR    WEIGHT    OF    THE    OLEFINS 

In  Fig.  23  the  mean  molecular  weight  of  the  olefin 
hydrocarbons  in  gases  made  at  825°  C.  in  oil-gas 
runs  and  in  hydrogen-oil-gas  runs  with  the  concentra- 
tion ratio  i Hz  :  2  Gas  can  be  seen. 

It  should  be  kept  in  mind  that  the  molecular  weight 
of  ethylene  is  28  and  that  of  propylene  is  42.  From 
the  position  of  the  curves  it  can  be  seen  that  ap- 
proximately one-third  of  the  olefins  is  propylene. 
The  curves  lie  very  close  together,  and  it  is  impossible 
to  say  just  what  the  influence  of  the  hydrogen  is  on 
the  formation  of  the  olefins. 

If  the  method  of  calculation  of  the  molecular  weight 
of  the  olefins,  as  explained  under  the  discussion  of  the 
analytical  methods,  is  considered,  it  is  apparent  that 
all  the  analytical  errors  pile  up  and  are  brought  out 
in  this  calculation.  This  no  doubt  accounts  for  the 
irregularity  in  the  curve,  and  also  for  the  fact  that 
there  is  no  consistent  difference  in  the  position  for  the 
oil-gas  run  and  the  hydrogen-oil-gas  runs. 

It  was  thought  that  certain  differences  might  be 
brought  to  light  by  the  curves  for  the  mean  molecular 
weights  of  the  olefins.  If  the  higher  olefins  were  more 
easily  hydrogenated  than  ethylene  the  curve  for  the 

(81) 


mean  molecular  weight  of  the  olefins  in  the  hydrogen- 
oil-gas  runs  would  fall  below  that  of  the  oil  runs. 
If,  on  the  other  hand,  the  presence  of  the  hydrogen,  on 
account  of  its  causing  a  more  rapid  passage  of  the  gas 
through  the  tube,  resulted  in  a  less  extensive  decom- 
position of  the  higher  olefins,  the  curve  for  the  hy- 
drogen-oil-gas  runs  would  lie  above  that  for  the  oil- 
gas  runs. 

It  may  be  thought  that  these  two  effects  are  balanc- 
ing each  other  with  the  result  that  the  curves  are 
practically  the  same.  It  would  have  been  desirable 
to  have  carried  out  a  similar  series  of  runs  with  a  high 
concentration  of  hydrogen,  but  the  calculation  of  the 
mean  molecular  weight  of  the  olefins  can  be  made  only 
when  the  per  cent  of  benzene  in  the  gas  is  known,  and, 
as  has  been  noted,  the  method  for  the  determination 
of  benzene  was  found  only  as  this  experimental  work 
was  drawing  to  a  close. 

THE  FORMATION  OF  AROMATIC  HYDROCARBONS 

Fig.  24  shows  the  percentage  of  aromatic  hydro- 
carbons present  in  the  gases  made  at  825°  C.  when 
oil  is  cracked  alone  or  in  hydrogen  when  the  con- 
centration ratio  is  iH2  :  2  (Oil  Gas  +  Tar  Gas).  The 
method  of  determining  these  percentages  "has  been 
described  under  the  analytical  methods. 

The  percentage  of  aromatics  appears  to  increase 
slightly  with  increase  in  oil  rate.  Whether  this  is 
actually  the  case  or  not  cannot  be  definitely  stated. 
The  exact  opposite  would  be  expected.  It  is  thought 
that  the  apparent  increase  may  be  due  to  the  freezing 
out  of  high  molecular  weight  hydrocarbons  of  other 
types  than  the  aromatic  compounds.  High  molecular 
weight  paraffins  and  olefins  are  present  in  greater 
proportion  in  the  gases  made  at  high  oil  rates  than  in 
those  made  at  low  oil  rates. 

The  smaller  proportion  of  aromatic  hydrocarbons 
present  in  the  gases  made  at  low  oil  rates  may  possibly 
be  due  to  the  removal  of  benzene  to  form  compounds 
such  as  diphenyl,  naphthalene  and  anthracene,  which 
pass  largely  into  the  tars. 

The  hydrogen  apparently  has  little  effect  on  the 
formation  of  aromatics  at  low  oil  rates,  but  decreases 
the  aromatic  formation  somewhat  at  higher  oil  rates. 
This  is  possibly  due  to  the  retarding  effect  which  the 
presence  of  hydrogen  would  have  on  the  formation  of 
aromatics  or  hydroaromatics  by  condensation  re- 
actions. Less  gas  is  formed  from  the  oil  at  high  oil 

(82) 


10 

r/6. 

25 

.  

o 

60 

/ 

p  —  •— 

.—  ' 

o  

_^c* 

x' 
X 

"'" 

JO 

y 

prn 

^' 

0/7  C 

JflS 

0/7  C 

a5   * 

/£  - 



>c  U 

A 

, 

62/ 

'C 

///,: 

26C 

5 

0 

r 

; 

F         /O        /5       20        25        JO        35       40       45       JC 

0/7   Pate  -  cc.    per    minute.    - 

10 

60 

r/6. 

26 

^ 

^ 

^r 

^X 

X* 

JU 

/ 
/ 
/ 

X 

40 
30 

y 

'/ 

72 

re 

IH2 

:26 

(LS 

/' 

77 

J 

-c  C* 
/O 

0 

/ 

>^ 

f 

(9/7  < 
0/7  t 

?<25 

ids  •#• 

HI- 

__  _ 

(?/7 

r        /0        /J"      20       2J      30      JJ       ¥0       -/5      JC 

/^arc  •'  cc.    per    minute.    - 

IU 

60 

r/6 

21 

— 

fs 

r^^" 

r^^ 

. 

-f  O 

P^     / 

P 

30 
20 

/O 

r 

0 

723' 

/•     j 

1*4  • 

/6as 

y 

y 

x 

^/ 

7*  ° 

OH 
Oil 

0(2-5 

^ 



°" 

o// 

'        /O        15       2Q       2S       3O       3, 

Rate  -   cc.    p^r    minutt 

J"       40       45       J"< 

9            ....-_     -  -  -  —  - 

(83) 


rates  than  at  low  oil  rates,  and  as  a  consequence  the 
concentration  of  hydrogen  is  greater  at  high  oil  rates 
than  at  low  oil  rates. 

TARS 

The  tars  were  collected  from  the  tar  drip  and  the 
volume  measured.  This  volume  divided  by  the 
volume  of  the  total  oil  used  and  multiplied  by  100 
gives  the  percentages  of  tar  formed.  Figs.  25  to  29 
show  these  tar  percentages  for  both  oil-gas  and 
hydrogen-oil-gas  runs  plotted  against  the  oil  rate  at  the 
temperatures  indicated.  It  should  be  mentioned  that 
at  low  oil  rates  these  percentages  are  not  accurate. 
The  low-oil-rate  tars  are  heavy  and  viscous,  and  as  a 
result  do  not  run  down  through  the  condenser  as 
easily  as  the  lighter  high-oil-rate  tars. 

As  far  as  can  be  judged  from  the  curves  in  Figs. 
25,  26,  and  27,  for  temperatures  of  621°  C.  and  723°  C. 
there  is  no  marked  regular  difference  between  the  tar 
formation  in  the  oil-gas  runs  and  the  hydrogen-oil- 
gas  runs. 

At  825°  C.  the  percentage  of  tar  in  the  oil-hydrogen 
runs  is  consistently  less  than  in  the  oil  runs  except  at 
low  oil  rates  where,  as  has  been  mentioned,  the  tar 
percentages  as  shown  mean  little.  This  difference  is 
more  marked  in  the  curves  of  Fig.  26  where  the  con- 
centration ratio  was  2  Hydrogen:  i  (Oil  Gas  +  Tar 
Gas)  than  in  the  curves  of  Fig.  28. 

In  general  two  classes  of  compounds  are  contained  in 
the  tar:  first,'  Unchanged  or  partially  changed  oil; 
second,  synthetic  hydrocarbons  which  are  the  products 
of  extensive  change.  It  may  be  thought  that  hy- 
drogen, on  account  of  its  decreasing  the  time  of  contact 
of  the  hydrocarbon  vapors  with  the  heated  tube, 
would  tend  to  increase  the  proportion  of  tar  since  the 
decrease  in  the  time  of  heating  would  cause  a  less 
extensive  decomposition  of  the  oil  vapors.  On  the 
other  hand,  this  decrease  in  the  time  of  heating  would 
also  diminish  the  extent  to  which  synthetic  reactions 
resulting  in  the  formation  of  tarry  products  would 
take  place.  Also  the  percentages  of  the  hydrogen 
would  retard  these  reactions,  since  they  are  all  re- 
actions which  result  in  decrease  of  volume.  Ap- 
parently these  effects  are  balanced  at  temperatures 
of  723°  C.  or  below.  At  825°  C.,  however,  the  per- 
centage of  tar  is  less.  This  leads  to  the  belief  that 
synthetic  reactions  are  responsible  for  a  considerable 
proportion  of  the  tars  at  temperatures  in  the  neighbor- 
hood of  825°  C. 

(84) 


/  u 

r  n 

r/6 

2Q 

50 

40 

1  (-\ 

825 

't 

!H2: 

2Gc 

5 

Oi 

Oil 

Ga. 

6as 

/  ^ 

•     _ 

_  _  _ 

20 

i  n 

*-n 

>£ 

•V 

^o- 

_ 

•Tl 

—  -1 

,  • 

.—  •  —  • 

0 

• 

J 

0/7 

IO         15       20        25       JO        35       4J       45        5(. 

Rate  -  cc.  per   minute.    - 

fO 

60 
SO 
AO 
30 

°0 

riG 

29 

82 

5'C 

21- 

{•I 

S.<25 

on 
on 

Gas 
Gas 

*/«• 



/o 

^ 

1  0  

i  . 

0  ' 

,  —  •— 

1 

7 

V- 

*o  



—<>• 

0  5          JO         15        20         25         JO         35        4O 

Oil   Rate  -  cc.  per    minute   • 


j>0 


is    funs 


10          15         20         25         3O         35         4O       4 

Oil    Rate   -  cc.    per  minute  - 

(85) 


Fig.  30  shows  clearly  the  effect  of  temperature  on 
tar  formation,  and  also  the  effect  of  increase  of  oil 
rate  at  constant  temperature.  The  proportion  of  tar 
increases  with  increasing  oil  rate  and  most  markedly 
so,  at  temperatures  of  621°  C.  and  723°  C.  The 
largest  proportion  of  these  tars  at  moderate  to  high 
oil  rates  is  undecomposed  oil,  as  shown  by  distillation 
and  treatment  with  concentrated  sulfuric  acid.  This 
is  also  indicated  by  the  fact  that  a  temperature  change 
from  621°  C.  to  723°  C.  produces  no  great  difference 
in  tar  formation,  and  also  by  the  fact  of  the  very  rapid 
increase  in  the  percentage  of  tar  with  increasing  oil 
rate. 

At  825°  C.  the  proportion  of  tar  does  not  increase 
greatly  with  increasing  oil  rate,  indicating  that  these 
tars  are  largely  composed  of  synthetic  products, 
which  is  further  substantiated  by  other  physical 
characteristics,  such  as  distinct  aromatic  odor  and 
their  reactions  with  concentrated  sulfuric  acid. 

All  the  tars  were  strongly  fluorescent. 

FORMATION    OF    ILLUMINANTS,    METHANE,    AND    ETHANE, 
AND     THE     OBTAINING     OF     PARTICULAR     END-PROD- 
UCTS   FROM    A    PARAFFIN    HYDROCARBON    OIL 

In  Figs.  31  to  35  the  cc.  of  illuminants,  methane  and 
ethane  formed  from  i  cc.  of  oil  are  shown  plotted 
against  the  oil  rate  at  the  temperatures  and  hydrogen- 
gas  concentration  ratios  indicated.  It  can  be  seen 
from  Fig.  31  that  at  621°  C.,  with  the  exception  of  the 
illuminants  in  the  case  of  the  straight  oil-gas  runs,  the 
number  of  cc.  of  all  these  hydrocarbons  formed  from 
i  cc.  of  oil  increases  with  decreasing  oil  rate.  There 
would  be  a  limit  to  this,  however,  for,  were  the  oil  rate 
made  low  enough,  a  very,  extensive  decomposition  of 
the  hydrocarbons  would  set  in. 

Fig.  31  shows  that  the  illuminants  are  the  most 
easily  decomposed  of  the  gaseous  hydrocarbons.  The 
curve  for  the  illuminants  in  the  straight  oil-gas  runs 
has  a  maximum  due  to  the  fact  that  though  the 
longer  time  of  contact  of  the  oil  vapors  with  the 
heated  tube  at  low  oil  rates  causes  a  more  extensive 
formation  of  ethylene  and  other  illuminants,  an  oil 
rate  is  reached  where  extensive  decomposition  of  these 
hydrocarbons  takes  place,  which  more  than  overcomes 
the  more  rapid  illuminants  formation  at  low  oil  rates. 
Condensation  and  hydrogenation,  which  are  more 
extensive  at  low  oil  rates,  are  important  in  this  con- 
nection also. 

(86) 


__  JOO 

6 

o  250 

VJ 

V, 


200 


Q./OO 


50 


O// 


-as 


Gas 


350 


Oil    Pate   -  cc.  per  minute 


0/7     Rate    -  cc.   per  minute 


4(J(J 
T  *\n 

f 

\ 

12? 

c.    ^ 

!/4s 

16^ 

250 
200 

^0 
0 

\ 

\ 

nc 

.JJ 

V 

f- 

\ 

V 

Oil  ( 

Oil  ( 

~as  1 

•^*- 



-   6 

V 

A 

~^\   6 

0 

V^ 

6 

^ 

•ST" 

£,— 

^: 

aa-**^ 

»  —  » 

L_ 

A 

"•6*.  „ 

"•^A 

^ 

r,H, 

"^ 

Oil 

/O         /5        20        25         30        JJ        40        45        5C 

Rate    -   cc.    per    minute   - 

(87) 


No  maximum  is  observed  in  the  illuminants  curve 
for  the  hydrogen  runs,  doubtless  because  the  time  of 
contact  of  the  oil  vapors  with  the  heated  tube  is  less 
at  any  particular  oil  rate  than  in  the  case  of  the  oil- 
gas  runs.  The  curve  for  the  illuminants  in  the  hy- 
drogen-oil-gas  runs,  for  this  reason  also,  is  always  be- 
low that  for  the  illuminants  in  the  oil-gas  runs,  except 
at  low  oil  rates. 

Less  methane  is  formed  per  cc.  of  oil  in  the  hy- 
drogen-oil-gas  runs  than  in  the  straight  oil-gas  runs 
except  at  low  oil  rates.  That  the  time  of  contact  here 
is  sufficient  so  that  extensive  hydrogenation  takes 
place  is  clearly  brought  out  from  a  consideration  of 
Fig.  22  in  connection  with  Fig.  31.  At  all  oil  rates 
the  decreased  time  of  contact  of  the  gases  with  the 
heated  furnace  tube,  on  account  of  the  absorption  of 
hydrogen,  results  in  a  lower  formation  of  methane. 

The  relationships  for  ethane  are  much  the  same  as 
for  methane,  and  for  the  same  reasons. 

Figs.  32  and  33  show  the  relationships  between  the 
hydrocarbons  at  723°  C.  at  hydrogen  concentration 
ratios  of  i/72  :  2  Gas  and  2#2  :  i  Gas,  respectively. 
More  of  each  of  the  components  is  formed  per  cc.  of 
oil  at  723°  C.  than  at  621°  C.  The  maximum  in  the 
illuminants  curve  falls  at  a  higher  oil  rate  than  at 
621°  C.  as  would  be  expected,  since  the  higher  tem- 
perature would  cause  a  more  rapid  decomposition, 
condensation,  and  hydrogenation  of  the  illuminants  to 
take  place.  At  723°  C.  the  maximum  on  the  illu- 
minants curve  for  the  hydrogen  runs  can  be  seen 
clearly.  It  is  interesting  to  note  that  this  falls  to  the 
left  of  the  maximum  on  the  curve  for  the  oil-gas  runs. 
The  decreased  time  of  heating  on  account  of  the 
hydrogenation  admixture  is  responsible  for  this. 

The  effect  on  the  illuminants  of  increasing  the  con- 
centration of  hydrogen  is  clearly  brought  out  in  Figs. 
32  and  33.  The  maximum  on  the  curve  for  the 
illuminants  in  the  hydrogen-oil-gas  runs  at  the  higher 
hydrogen  concentration  falls  at  a  slightly  lower  oil 
rate  than  the  maximum  on  the  curve  for  the  lower 
hydrogen  concentration.  The  divergence  between  the 
illuminants  curves  for  the  oil-gas  runs  and  the  hy- 
drogen-oil-gas  runs  is  greater  both  at  low  and  high  oil 
rates  at  the  higher  hydrogen  concentration  than  at  the 
lower  hydrogen  concentration  on  the  time  of  contact 
•of  the  gases  with  the  heated  tube  surfaces. 

The  relationships  in  the  case  of  the  methane  and 
ethane  are  exceedingly  interesting.  The  formation 

(88) 


60D 


550 


TO          15         20        <eJ         JO         JO         40        ^7         TO 

£//    P^?(?    -    tc.   per    minute  - 


JPV 

J     450 

."^   400 
0 

<o    35"0 
*0 

V..   JOO 

sc 

2JO 

•t-K 

s: 

<0     200 

c 

O 

^  /5° 

t: 
o 

^      700 

VJ 
VO      SO 

V 

823 

°c 

ZH2>. 

/  COL 

* 

1 

\ 
\ 

rk 

;.  jj 

\ 

vd 

^  ,- 

t 

N 

A 

0 
Oi 

'/  6a 

f  Ga 

5 
5     +1- 

6  - 

o 

6 

A 

<\. 

^ 

/ 
/ 

/ 

\\v* 

\ 

r^I 
^x 

^ 

2 

2 

> 

^ 

^^ 

^. 

^ 

/ 

^- 

^ 

4?,! 

^5:" 

-o—o-l 

•«  — 

~t>  — 

C&l. 

Oil    Rate    -   cc.  per    minute 


(89) 


of  methane  is  less  in  the  hydrogen-oil-gas  runs  than 
in  the  oil-gas  runs  at  moderate  to  high  oil  rates,  due 
to  the  decreased  time  of  contact  of  the  gases  witty  the 
heated  surfaces,  and  this  effect  is  more  pronounced 
at  the  higher  hydrogen  concentrations,  as  would  be 
expected.  As  the  oil  rate  decreases  the  hydrogenation 
effect  becomes  important  and  the  proportion  of 
methane  formed  from  i  cc.  of  oil  is  greatest  in  the 
case  of  the  hydrogen-oil-gas  runs.  The  curve  for 
methane  in  the  hydrogen-oil-gas  runs  crosses  the 
methane  curve  for  the  oil-gas  runs.  This  crossing 
is  at  a  higher  oil  rate  with  the  higher  hydrogen  con- 
centration, showing  clearly  the  effect  of  the  increase 
of  concentration  of  hydrogen  on  the  hydrogenation 
reactions.  The  formation  of  methane  is  slightly 
greater  in  the  hydrogen-oil-gas  runs  than  in  the 
straight  oil-gas  runs  when  the  hydrogen  concentration 
ratio  is  iHz  :  2  Gas.  This  difference  is  slightly 
greater  at  low  oil  rates  than  at  high  oil  rates. 

When  the  hydrogen  concentration  ratio  is  2#2  •'  i 
Gas  the  ethane  formation  per  cc.  of  oil  is  less  in  the 
hydrogen-oil-gas  runs  than  in  the  oil-gas  runs  at 
high  oil  rates.  This  is  the  effect  of  the  decreased  time 
of  contact  due  to  the  admixture  of  a  larger  volume  of 
hydrogen.  But  at  low  oil  rates  the  formation  of 
ethane  is  much  greater  in  the  hydrogen-oil-gas  runs 
as  can  be  seen  in  Fig.  33.  The  ethane  curve  has  a 
maximum,  too,  which  is  interesting  because  it  shows 
that  at  low  oil  rates  the  reactions  of  the  hydrocarbon 
ethane  itself  have  an  important  part  to  play.  . 

Figs.  34  and  35  show  the  relationships  between  these 
hydrocarbons  at  825°  C.  A  much  less  pronounced 
decrease  in  the  formation  of  illuminants  with  in- 
creasing oil  rate  is  due  to  the  fact  that  the  temperature 
of  825°  C.  is  sufficient  to  promote  actively  the  forma- 
tion of  illuminants.  The  maxima  on  the  illuminants 
curves  for  the  oil-gas  runs  fall  at  the  higher  oil  rates, 
as  would  be  expected  when  the  higher  temperature  is 
taken  into  consideration.  The  illuminants  curves  for 
the  hydrogen-oil-gas  runs  are  entirely  above  the 
illuminants  curves  for  the  oil-g'as  runs.  This  is  again 
a  result  of  the  decreased  time  of  heating  when  hy- 
drogen is  admixed.  The  effect  is  most  marked  when 
the  higher  concentration  of  hydrogen  is  used. 

The  curves  for  methane  in  the  hydrogen-oil-gas  runs 
fall  above  the  curves  for  methane  in  the  oil-gas  runs 
at  all  oil  rates  at  825°  C.  This  is  due  to  two  effects: 
first,  the  less  extensive  decomposition  of  the  methane 

(90) 


into  carbon  and  hydrogen  due  to  the  decreased  time  of 
heating  in  the  hydrogen-oil-gas  runs;  second,,  the 
increased  rate  of  hydrogenation  reactions  such  as 
C2H4  +  2H2  "*"V  2CH4.  The  effect  of  hydrogen  in 


JOO 
450 
400 
*    JJO 


zoo 


zso 


£  200 

^ 
o 
Q.  ISO 

o 

Vj    /OO 


so 


600 


TOO 


600 


nc.  J6 


OH    (>45 


Runs 


Oil    Rate    -    cc.    per    minute 


^soo 


+  400 


O  JOO 


200 


/OO 


\J 

Vo 


Oil     Rate   -  cc    per    minute.   -    — - 
reversing  the  reaction   CH4  ~*~^  C  +  2H2  is  probably 
not  important,   as   has   been   brought   out   in   the   dis- 
cussion of  the  methane  equilibrium  and  the  reactions 
of  methane  in  the  first  part  of  this  paper. 

(91) 


The  effect  of  the  greater  concentration  of  hydrogen 
on  methane  production  can  be  seen  clearly  by  com- 
paring Figs.  34  and  35.  The  divergence  between  the 
hydrogen-oil-gas  and  the  oil-gas  methane  curves  is 
greatest  when  the  hydrogen  concentration  ratio  is 
2 #2  :  i  Gas,  and  this  is  practically  true  at  low  oil 
rates  where  hydrogenation  reactions  are  most  im- 
portant. 

More  ethane  is  formed  when  hydrogen  is  mixed  with 
the  vapors  of  the  oil  than  when  it  is  not  added.  This 
is  doubtless  due  to  the  combined  influence  of  the 
hydrogen  in  diminishing  the  decomposition  of  the 
ethane  and  to  its  effect  in  hydrogenating  the  olefins. 
These  effects  are  particularly  marked  when  the  con- 
centration ratio  is  2H2  :  i  Gas. 

It  may  have  been  noticed  that  the  curves  for  the 
oil-gas  runs  made  at  the  same  temperature  do  not 
coincide  exactly,  since  the  carbon  tube  used  car- 
bonizes somewhat  and  becomes  of  smaller  internal 
diameter,  thus  decreasing  the  time  of  contact  of  the 
gas  with  the  tube  and  consequently  altering  the  com- 
position somewhat. 

The  effect  of  temperature  on  the  hydrocarbon 
products  of  decomposition  of  an  oil  can  be  seen  very 
clearly  from  Fig.  36.  Within  the  temperature  range 
studied,  the  cc.  of  illuminants  per  cc.  of  oil  increases 
with  temperature,  with  one  exception.  At  low  oil 
rates  there  are  more  illuminants  formed  at  723°  C. 
than  at  825°  C.  The  effect  of  the  higher  temperature 
in  increasing  the  speed  of  the  reactions  which  de- 
compose ethylene  more  than  overcomes  the  effect  of 
the  higher  temperatures  in  promoting  the  decom- 
position of  the  long  chain  olefins  to  ethylene  and 
propylene. 

It  is  interesting  to  note  the  position  of  the  maxima 
of  the  curves  for  the  illuminants  at  the  several  tem- 
peratures. These  maxima  indicate  where  the  balance 
between  the  reactions  of  formation  and  the  reactions 
of  decomposition  falls. 

Within  the  temperature  range  studied,  the  forma- 
tion of  methane  is  greater  the  higher  the  temperature. 
At  low  oil  rates  the  difference  in  the  methane  pro- 
duced by  a  ioo°-temperature  rise  is  greater  in  the 
range  from  621  to  723°  C.  than  from  723  to  825°  C., 
since  at  low  oil  rates  723°  C.  is  a  sufficiently  "high 
temperature  to  break  down  the  original  oil  extensively. 
The  methane  increase  between  723  and  825°  C.  is 
largely  due  to  the  decomposition  and  hydrogenation  of 

(92) 


olefins  C2H4  — >  C  +  CH4  and  C2H4  +  2H2  ±J 
2CH4,  as  can  be  seen  from  a  consideration  of  the 
illuminants  curve  for  825°.C. 

At  high  oil  rates  a  temperature  of  825°  C.  is  neces- 
sary to  form  methane  largely,  as  can  be  seen  from  the 
position  of  the  curve  for  methane  at  621,  723  and 
825°  C. 

The  formation  of  ethane  per  cc.  of  oil  is- not  large  at 
any  temperature  studied,  as  shown  in  Fig.  36.  The 
primary  decomposition  of  the  oil  therefore  involves 
chiefly  a  splitting  off  of  methane  rather  than  ethane 
or  higher  paraffin.  The  decomposition  and  dissocia- 
tion of  ethane  are  clearly  shown  by  the  falling  off  of 
the  ethane  curve  as  the  oil  rate  decreases  at  a  tem- 
perature of  825°  C.  On  the  other  hand,  a  tem- 
perature of  825°  C.  is  necessary  to  cause  an  extensive 
formation  of  methane  and  ethane  per  cc.  of  oil  at  high 
^oil  rates. 

TOTAL    HYDROCARBONS    OBTAINABLE    FROM    THE    OIL 

The  greater  the  proportion  of  the  carbon  of  the  oil 
which  can  be  obtained  in  gaseous  form  the  better  the 
utilization  of  the  oil  for  gas-making  purposes. 

Fig.  37  shows  the  Total  cc.  of  Illuminants  +  methane 
+  ethane  obtainable  from  i  cc.  of  oil  under  the  varying 
conditions.  At  62i°C.  more  hydrocarbons  are  ob- 
tained per  cc.  of  oil  in  the  oil-gas  runs  than  in  the 
hydrogen-oil-gas  runs,  except  at  low  oil  rates  where 
hydrogenation  reactions  become  important.  This  is 
due  to  the  lower  time  of  contact  of  the  oil  vapors  with 
the  furnace  tube  in  the  case  of  the  hydrogen-oil-gas 
runs.  The  same  relations  hold  at  723°  C.  except 
that  the  hydrogen-oil-gas  curves  cross  the  oil-gas 
curve  at  a  higher  oil  rate  because  of  the  greater  effect 
of  the  higher  temperature  in  hastening  the  hydrogena- 
tion reactions.  The  effect  of  the  higher  concentration 
of  hydrogen  is  clearly  shown.  At  825°  C.  the  hy- 
drocarbons formed  per  cc.  of  oil  are  of  greater  volume 
in  the  hydrogen-oil-gas  runs  at  all  oil  rates  studied. 
The  higher  temperature  promotes  hydrogenation  re- 
actions at  all  oil  rates.  The  effect  of  the  greater 
concentration  of  hydrogen  can  be  seen. 

It  is  interesting  to  note  that  the  slope  of  the  curve 
for  the  hydrogen-oil-gas  runs  at  723°  C.  is  much 
steeper  than  the  slope  of  these  curves  at  825°  C.  at 
low  oil  rates,  doubtless  because  at  825°  C.,  and  low 
oil  rates,  dehydrogenation  reactions  and  reactions  of 
decomposition  of  the  hydrocarbons  become  of  im- 
portance. 

(93) 


SUMMARY 

i— A  critical  review  of  the  most  important  work  on 
hydrocarbon  decomposition  and  the  influence  of 
hydrogen  on  the  reactions  involved  has  been  given. 
This  has  concerned  itself  with:  first,  the  hydrocarbons 
of  high  molecular  weight;  second,  the  products  of  the 
primary  decomposition;  and  third,  the  reactions  of  the 
simpler  hydrocarbons.  Summaries  have  been  in- 
cluded which  state  concisely  the  probable  course  of  the 
reactions  of  dissociation,  decomposition,  and  condensa- 
tion involved. 

2 — The  subject  of  the  mechanism  of  heat  transfer 
in  gas  machines  has  been  discussed. 

3 — Difficulties  in  the  measurement  of  the  true  tem- 
perature of  a  gas  have  been  pointed  out. 

4 — In  the  experimental  work  a  paraffin  oil  was 
thermally  decomposed  alone  and  in  hydrogen  at 
temperatures  of  621,  723  and  825°  C.  Concentra- 
tions of  hydrogen  approximating  i//2  :  2  Oil  Gas  and 
2 H2  :  i  Oil  Gas  were  those  studied.  It  has  been 
shown  what  results  may  be  expected  in  the  decom- 
position of  a  hydrocarbon  oil  when  temperature,  rate 
of  oil  feed,  and  concentration  of  admixed  hydrogen 
are  carefully  controlled. 

5 — The  relationship  between  the  rate  of  oil  feed  and 
the  rate  of  gas  generation  has  been  brought  out. 

6 — The  proportions  of  illuminants,  saturated  hy- 
drocarbons, and  hydrogen  resulting  at  varying  rates 
of  oil  feed,  and  at  temperatures  of  621,  723  and 
825°  C.  have  been  shown  graphically  and  discussed. 

7 — The  effects  of  hydrogen  on  the  reactions  which 
give  rise  to  saturated  hydrocarbons  and  illuminants 
have  been  shown  graphically  and  discussed  at  some 
length.  Besides  its  effect  in  hydrogenating  olefins 
and  other  hydrocarbons,  the  hydrogen,  since  its  addi- 
tion causes  an  increase  in  the  total  volume  of  the  gas 
passing  through  the  heated  zone  of  the  furnace  in  a 
given  time,  decreases  the  time  of  contact  of  the  gases 
with  the  heated  walls  of  the  resistor  tube.  The 
effects  of  this  are  discussed  in  connection  with  the 
curves  showing  the  relationships  between  the  com- 
ponents of  the  gas  when  the  oil  is  cracked  in  hydrogen. 

8 — The  mean  molecular  weight  of  the  olefins  in  a 
series  of  gases  made  at  825°  C.  has  been  determined, 
and  also  the  proportion  of  aromatic  hydrocarbons 
in  these  gases. 

(94) 


9 — The  formation  of  tar  was  studied  at  the  various 
oil  rates,  temperatures  and  concentrations  of  hy- 
drogen. 

10 — Curves  showing  the  number  of  cc.  of  illuminants, 
ethane,  and  methane  obtainable  from  i  cc.  of  oil  have 
been  shown. 

ii — In  general  the  manner  of  decomposition  of  a 
paraffin  hydrocarbon  oil  has  been  mapped  out  over  a 
considerable  range  of  temperature,  rate  of  oil  feed, 
and  concentration  of  hydrogen. 

12 — The  results  recorded  in  this  paper  may  serve 
as  a  guide  to  the  obtaining  of  more  desirable  results  in 
commercial  operations  involving  the  decomposition  of 
oil  for  gas-making  purposes. 

CONCLUSIONS 

In  addition  to  showing  the  proportions  of  products 
which  are  obtainable  under  a  variety  of  conditions, 
which  relationships  have  been  fully  set  forth  in  the 
figures  shown  and  which  it  is  impossible  to  briefly 
summarize,  it  has  been  concluded  as  a  result  of  this  in- 
vestigation: 

I — That  the  importance  of  radiation  insofar  as  it  is 
concerned  in  the  furnishing  of  the  energy  for  the  pro- 
duction of  hydrocarbon  reactions  has  been  over- 
estimated. 

II — That  effects  often  ascribed  to  catalysis  are  in 
reality  due  to  effective  heat  transfer  by  conduction 
arid  convection  from  the  large  heated  surfaces  exposed 
to  the  gases. 

Ill — That  the  equilibrium  condition  is  not  attained 
in  a  hydrocarbon  system  when  an  oil  is  decomposed 
by  heat  under  conditions  analogous  to  those  of  car- 
bureted water-gas  manufacture. 

IV — That  the  course  of  the  changes  involved  in  the 
breaking  down  of  a  hydrocarbon  oil  may  be  roughly 
traced. 

V — That  hydrogen  is  produced  from  an  oil  even  when 
the  cracking  takes  place  in  hydrogen. 

VI — That  considerable  absorptions  of  hydrogen  take 
place  when  an  oil  is  cracked  in  an  atmosphere  of 
hydrogen,  and  this  absorption  is  greater  the  higher 
the  concentration  of  hydrogen,  the  higher  the  tem- 
perature (within  the  range  studied),  and  the  lower  the 
oil  rate. 

VII — That  propylene  and  higher  olefins  constitute 
approximately  one-third  by  volume  of  the  illuminants 
of  the  gas. 

(95) 


VIII — That  the  proportion  of  tar  increases  with  de- 
crease in  temperature,  and  with  increasing  oil  rate, 
particularly  at  the  lower  temperatures. 

IX — That  no  marked  and  consistent  difference  in  the 
amount  of  tar  formed  when  an  oil  is  decomposed  alone 
or  in  hydrogen  at  temperatures  of  723°  C.  or  below  is 
noticeable.  At  825°  C.  less  tar  is  formed  when  the 
oil  is  cracked  in  hydrogen.  The  tars  formed  below 
723°  C.  are  in  large  part  unchanged  or  partly  changed 
oil,  whereas  those  tars  formed  above  800°  C.  are 
essentially  composed  of  synthetic  products. 

X — That  the  reactions  which  result  in  decreasing 
the  proportion  of  illuminants  are  the  most  rapid. 

XI — That  the  presence  of  hydrogen  during  the  de- 
composition of  an  oil  has  the  effect  of  increasing 
largely  the  proportion  of  the  carbon  of  the  oil  ap- 
pearing as  hydrocarbons  in  the  gas. 

XII — That  within  the  temperature  range  studied 
the  volume  of  illuminants  produced  per  volume  of  oil 
increases  with  the  temperature  with  one  slight  ex- 
ception. The  formation  of  methane  is  greater  the 
higher  the  temperature.  The  formation  of  ethane  is 
not  large  at  any  temperature  and  therefore  the  primary 
decomposition  of  an  oil  involves  chiefly  a  splitting  off 
of  methane  rather  than  ethane  or  higher  homologs. 

XIII — That  a  temperature  of  823°  C.  is  desirable 
in  decomposing  an  oil  provided  that  too  great  op- 
portunity for  extensive  secondary  and  tertiary  change 
is  not  given. 

XIV — That  with  correct  design  of  apparatus,  and 
proper  adjustment  of  temperature,  rate  of  oil  feed, 
and  concentration  of  hydrogen  it  is  possible  to  obtain 
gases  of  widely  varying  compositions. 

DEPARTMENT  OF  CHEMICAL  ENGINEERING 
COLUMBIA  UNIVERSITY,  NEW  YORK  CITY 


(96) 


VITA 

Eugene  Hendricks  Leslie  was  born  at  Ottawa, 
Illinois,  August  28,  1892. 

He  was  graduated  from  the  Ottawa  High  School  in 
June,  1909,  and  in  the  Fall  of  that  year  he  entered  the 
University  of  Illinois.  From  this  institution  he  was 
graduated  in  June  of  the  year  191 J  with  the  degree  of 
Bachelor  of  Science  in  Chemical  Engineering. 

In  September,  1913,  he  entered  Columbia  University 
where  he  has  been  in  continuous  residence  to  this  date. 
During  this  time  he  has  been  engaged  in  graduate 
study  and  research  work  and  has  held  an  assistantship 
in  the  Department  of  Chemistry.  He  has  also  been  an 
officer  of  instruction  in  the  intervening  summer  sessions 
at  Columbia,  and  in  Extension  Teaching. 


UNIVEESITY  OF  CALIFOENIA  LIBEAEY 
BEEKELEY 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 

Books  not  returned  on  time  are  subject  to  a  fine  of 
50c  per  volume  after  the  third  day  overdue,  increasing 
to  $1.00  per  volume  after  the  sixth  day.  Books  not  in 
demand  may  be  renewed  if  application  is  made  before 
expiration  of  loan  period. 


^26  t910 
APK   8    ls»24 


50m-7,'16 


YC   '3370 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


